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rfc:rfc2445

Network Working Group F. Dawson Request for Comments: 2445 Lotus Category: Standards Track D. Stenerson

                                                            Microsoft
                                                        November 1998
   Internet Calendaring and Scheduling Core Object Specification
                            (iCalendar)

Status of this Memo

 This document specifies an Internet standards track protocol for the
 Internet community, and requests discussion and suggestions for
 improvements.  Please refer to the current edition of the "Internet
 Official Protocol Standards" (STD 1) for the standardization state
 and status of this protocol.  Distribution of this memo is unlimited.

Copyright Notice

 Copyright (C) The Internet Society (1998).  All Rights Reserved.

Abstract

 There is a clear need to provide and deploy interoperable calendaring
 and scheduling services for the Internet. Current group scheduling
 and Personal Information Management (PIM) products are being extended
 for use across the Internet, today, in proprietary ways. This memo
 has been defined to provide the definition of a common format for
 openly exchanging calendaring and scheduling information across the
 Internet.
 This memo is formatted as a registration for a MIME media type per
 [RFC 2048]. However, the format in this memo is equally applicable
 for use outside of a MIME message content type.
 The proposed media type value is 'text/calendar'. This string would
 label a media type containing calendaring and scheduling information
 encoded as text characters formatted in a manner outlined below.
 This MIME media type provides a standard content type for capturing
 calendar event, to-do and journal entry information. It also can be
 used to convey free/busy time information. The content type is
 suitable as a MIME message entity that can be transferred over MIME
 based email systems, using HTTP or some other Internet transport. In

Dawson & Stenerson Standards Track [Page 1] RFC 2445 iCalendar November 1998

 addition, the content type is useful as an object for interactions
 between desktop applications using the operating system clipboard,
 drag/drop or file systems capabilities.
 This memo is based on the earlier work of the vCalendar specification
 for the exchange of personal calendaring and scheduling information.
 In order to avoid confusion with this referenced work, this memo is
 to be known as the iCalendar specification.
 This memo defines the format for specifying iCalendar object methods.
 An iCalendar object method is a set of usage constraints for the
 iCalendar object. For example, these methods might define scheduling
 messages that request an event be scheduled, reply to an event
 request, send a cancellation notice for an event, modify or replace
 the definition of an event, provide a counter proposal for an
 original event request, delegate an event request to another
 individual, request free or busy time, reply to a free or busy time
 request, or provide similar scheduling messages for a to-do or
 journal entry calendar component. The iCalendar Transport-indendent
 Interoperability Protocol (iTIP) defined in [ITIP] is one such
 scheduling protocol.

Table of Contents

 1 Introduction.....................................................5
 2 Basic Grammar and Conventions....................................6
  2.1 Formatting Conventions .......................................7
  2.2 Related Memos ................................................8
  2.3 International Considerations .................................8
 3 Registration Information.........................................8
  3.1 Content Type .................................................8
  3.2 Parameters ...................................................9
  3.3 Content Header Fields .......................................10
  3.4 Encoding Considerations .....................................10
  3.5 Security Considerations .....................................10
  3.6 Interoperability Considerations .............................11
  3.7 Applications Which Use This Media Type ......................11
  3.8 Additional Information ......................................11
  3.9 Magic Numbers ...............................................11
  3.10 File Extensions ............................................11
  3.11 Contact for Further Information: ...........................12
  3.12 Intended Usage .............................................12
  3.13 Authors/Change Controllers .................................12
 4 iCalendar Object Specification..................................13
  4.1 Content Lines ...............................................13
   4.1.1 List and Field Separators ................................16
   4.1.2 Multiple Values ..........................................16
   4.1.3 Binary Content ...........................................16

Dawson & Stenerson Standards Track [Page 2] RFC 2445 iCalendar November 1998

   4.1.4 Character Set ............................................17
  4.2 Property Parameters .........................................17
   4.2.1 Alternate Text Representation ............................18
   4.2.2 Common Name ..............................................19
   4.2.3 Calendar User Type .......................................20
   4.2.4 Delegators ...............................................20
   4.2.5 Delegatees ...............................................21
   4.2.6 Directory Entry Reference ................................21
   4.2.7 Inline Encoding ..........................................22
   4.2.8 Format Type ..............................................23
   4.2.9 Free/Busy Time Type ......................................23
   4.2.10 Language ................................................24
   4.2.11 Group or List Membership ................................25
   4.2.12 Participation Status ....................................25
   4.2.13 Recurrence Identifier Range .............................27
   4.2.14 Alarm Trigger Relationship ..............................27
   4.2.15 Relationship Type .......................................28
   4.2.16 Participation Role ......................................29
   4.2.17 RSVP Expectation ........................................29
   4.2.18 Sent By .................................................30
   4.2.19 Time Zone Identifier ....................................30
   4.2.20 Value Data Types ........................................32
  4.3 Property Value Data Types ...................................32
   4.3.1 Binary ...................................................33
   4.3.2 Boolean ..................................................33
   4.3.3 Calendar User Address ....................................34
   4.3.4 Date .....................................................34
   4.3.5 Date-Time ................................................35
   4.3.6 Duration .................................................37
   4.3.7 Float ....................................................38
   4.3.8 Integer ..................................................38
   4.3.9 Period of Time ...........................................39
   4.3.10 Recurrence Rule .........................................40
   4.3.11 Text ....................................................45
   4.3.12 Time ....................................................47
   4.3.13 URI .....................................................49
   4.3.14 UTC Offset ..............................................49
  4.4 iCalendar Object ............................................50
  4.5 Property ....................................................51
  4.6 Calendar Components .........................................51
   4.6.1 Event Component ..........................................52
   4.6.2 To-do Component ..........................................55
   4.6.3 Journal Component ........................................56
   4.6.4 Free/Busy Component ......................................58
   4.6.5 Time Zone Component ......................................60
   4.6.6 Alarm Component ..........................................67
  4.7 Calendar Properties .........................................73
   4.7.1 Calendar Scale ...........................................73

Dawson & Stenerson Standards Track [Page 3] RFC 2445 iCalendar November 1998

   4.7.2 Method ...................................................74
   4.7.3 Product Identifier .......................................75
   4.7.4 Version ..................................................76
  4.8 Component Properties ........................................77
   4.8.1 Descriptive Component Properties .........................77
     4.8.1.1 Attachment ...........................................77
     4.8.1.2 Categories ...........................................78
     4.8.1.3 Classification .......................................79
     4.8.1.4 Comment ..............................................80
     4.8.1.5 Description ..........................................81
     4.8.1.6 Geographic Position ..................................82
     4.8.1.7 Location .............................................84
     4.8.1.8 Percent Complete .....................................85
     4.8.1.9 Priority .............................................85
     4.8.1.10 Resources ...........................................87
     4.8.1.11 Status ..............................................88
     4.8.1.12 Summary .............................................89
   4.8.2 Date and Time Component Properties .......................90
     4.8.2.1 Date/Time Completed ..................................90
     4.8.2.2 Date/Time End ........................................91
     4.8.2.3 Date/Time Due ........................................92
     4.8.2.4 Date/Time Start ......................................93
     4.8.2.5 Duration .............................................94
     4.8.2.6 Free/Busy Time .......................................95
     4.8.2.7 Time Transparency ....................................96
   4.8.3 Time Zone Component Properties ...........................97
     4.8.3.1 Time Zone Identifier .................................97
     4.8.3.2 Time Zone Name .......................................98
     4.8.3.3 Time Zone Offset From ................................99
     4.8.3.4 Time Zone Offset To .................................100
     4.8.3.5 Time Zone URL .......................................101
   4.8.4 Relationship Component Properties .......................102
     4.8.4.1 Attendee ............................................102
     4.8.4.2 Contact .............................................104
     4.8.4.3 Organizer ...........................................106
     4.8.4.4 Recurrence ID .......................................107
     4.8.4.5 Related To ..........................................109
     4.8.4.6 Uniform Resource Locator ............................110
     4.8.4.7 Unique Identifier ...................................111
   4.8.5 Recurrence Component Properties .........................112
     4.8.5.1 Exception Date/Times ................................112
     4.8.5.2 Exception Rule ......................................114
     4.8.5.3 Recurrence Date/Times ...............................115
     4.8.5.4 Recurrence Rule .....................................117
   4.8.6 Alarm Component Properties ..............................126
     4.8.6.1 Action ..............................................126
     4.8.6.2 Repeat Count ........................................126
     4.8.6.3 Trigger .............................................127

Dawson & Stenerson Standards Track [Page 4] RFC 2445 iCalendar November 1998

   4.8.7 Change Management Component Properties ..................129
     4.8.7.1 Date/Time Created ...................................129
     4.8.7.2 Date/Time Stamp .....................................130
     4.8.7.3 Last Modified .......................................131
     4.8.7.4 Sequence Number .....................................131
   4.8.8 Miscellaneous Component Properties ......................133
     4.8.8.1 Non-standard Properties .............................133
     4.8.8.2 Request Status ......................................134
 5 iCalendar Object Examples......................................136
 6 Recommended Practices..........................................140
 7 Registration of Content Type Elements..........................141
  7.1 Registration of New and Modified iCalendar Object Methods ..141
  7.2 Registration of New Properties .............................141
   7.2.1 Define the property .....................................142
   7.2.2 Post the Property definition ............................143
   7.2.3 Allow a comment period ..................................143
   7.2.4 Submit the property for approval ........................143
  7.3 Property Change Control ....................................143
 8 References.....................................................144
 9 Acknowledgments................................................145
 10 Authors' and Chairs' Addresses................................146
 11 Full Copyright Statement......................................148

1 Introduction

 The use of calendaring and scheduling has grown considerably in the
 last decade. Enterprise and inter-enterprise business has become
 dependent on rapid scheduling of events and actions using this
 information technology. However, the longer term growth of
 calendaring and scheduling, is currently limited by the lack of
 Internet standards for the message content types that are central to
 these knowledgeware applications. This memo is intended to progress
 the level of interoperability possible between dissimilar calendaring
 and scheduling applications. This memo defines a MIME content type
 for exchanging electronic calendaring and scheduling information. The
 Internet Calendaring and Scheduling Core Object Specification, or
 iCalendar, allows for the capture and exchange of information
 normally stored within a calendaring and scheduling application; such
 as a Personal Information Manager (PIM) or a Group Scheduling
 product.
 The iCalendar format is suitable as an exchange format between
 applications or systems. The format is defined in terms of a MIME
 content type. This will enable the object to be exchanged using
 several transports, including but not limited to SMTP, HTTP, a file
 system, desktop interactive protocols such as the use of a memory-
 based clipboard or drag/drop interactions, point-to-point
 asynchronous communication, wired-network transport, or some form of

Dawson & Stenerson Standards Track [Page 5] RFC 2445 iCalendar November 1998

 unwired transport such as infrared might also be used.
 The memo also provides for the definition of iCalendar object methods
 that will map this content type to a set of messages for supporting
 calendaring and scheduling operations such as requesting, replying
 to, modifying, and canceling meetings or appointments, to-dos and
 journal entries. The iCalendar object methods can be used to define
 other calendaring and scheduling operations such a requesting for and
 replying with free/busy time data. Such a scheduling protocol is
 defined in the iCalendar Transport-independent Interoperability
 Protocol (iTIP) defined in [ITIP].
 The memo also includes a formal grammar for the content type based on
 the Internet ABNF defined in [RFC 2234]. This ABNF is required for
 the implementation of parsers and to serve as the definitive
 reference when ambiguities or questions arise in interpreting the
 descriptive prose definition of the memo.

2 Basic Grammar and Conventions

 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY" and
 "OPTIONAL" in this document are to be interoperated as described in
 [RFC 2119].
 This memo makes use of both a descriptive prose and a more formal
 notation for defining the calendaring and scheduling format.
 The notation used in this memo is the ABNF notation of [RFC 2234].
 Readers intending on implementing this format defined in this memo
 should be familiar with this notation in order to properly interpret
 the specifications of this memo.
 All numeric and hexadecimal values used in this memo are given in
 decimal notation.
 All names of properties, property parameters, enumerated property
 values and property parameter values are case-insensitive. However,
 all other property values are case-sensitive, unless otherwise
 stated.
      Note: All indented editorial notes, such as this one, are
      intended to provide the reader with additional information. The
      information is not essential to the building of an
      implementation conformant with this memo. The information is
      provided to highlight a particular feature or characteristic of
      the memo.

Dawson & Stenerson Standards Track [Page 6] RFC 2445 iCalendar November 1998

 The format for the iCalendar object is based on the syntax of the
 [RFC 2425] content type. While the iCalendar object is not a profile
 of the [RFC 2425] content type, it does reuse a number of the
 elements from the [RFC 2425] specification.

2.1 Formatting Conventions

 The mechanisms defined in this memo are defined in prose. Many of the
 terms used to describe these have common usage that is different than
 the standards usage of this memo. In order to reference within this
 memo elements of the calendaring and scheduling model, core object
 (this memo) or interoperability protocol [ITIP] some formatting
 conventions have been used. Calendaring and scheduling roles are
 referred to in quoted-strings of text with the first character of
 each word in upper case. For example, "Organizer" refers to a role of
 a "Calendar User" within the scheduling protocol defined by [ITIP].
 Calendar components defined by this memo are referred to with
 capitalized, quoted-strings of text. All calendar components start
 with the letter "V". For example, "VEVENT" refers to the event
 calendar component, "VTODO" refers to the to-do calendar component
 and "VJOURNAL" refers to the daily journal calendar component.
 Scheduling methods defined by [ITIP] are referred to with
 capitalized, quoted-strings of text. For example, "REQUEST" refers to
 the method for requesting a scheduling calendar component be created
 or modified, "REPLY" refers to the method a recipient of a request
 uses to update their status with the "Organizer" of the calendar
 component.
 The properties defined by this memo are referred to with capitalized,
 quoted-strings of text, followed by the word "property". For example,
 "ATTENDEE" property refers to the iCalendar property used to convey
 the calendar address of a calendar user. Property parameters defined
 by this memo are referred to with lowercase, quoted-strings of text,
 followed by the word "parameter". For example, "value" parameter
 refers to the iCalendar property parameter used to override the
 default data type for a property value. Enumerated values defined by
 this memo are referred to with capitalized text, either alone or
 followed by the word "value". For example, the "MINUTELY" value can
 be used with the "FREQ" component of the "RECUR" data type to specify
 repeating components based on an interval of one minute or more.

Dawson & Stenerson Standards Track [Page 7] RFC 2445 iCalendar November 1998

2.2 Related Memos

 Implementers will need to be familiar with several other memos that,
 along with this memo, form a framework for Internet calendaring and
 scheduling standards. This memo, [ICAL], specifies a core
 specification of objects, data types, properties and property
 parameters.
 [ITIP] - specifies an interoperability protocol for scheduling
 between different implementations;
 [IMIP] specifies an Internet email binding for [ITIP].
 This memo does not attempt to repeat the specification of concepts or
 definitions from these other memos. Where possible, references are
 made to the memo that provides for the specification of these
 concepts or definitions.

2.3 International Considerations

 In the rest of this document, descriptions of characters are of the
 form "character name (codepoint)", where "codepoint" is from the US-
 ASCII character set. The "character name" is the authoritative
 description; (codepoint) is a reference to that character in US-ASCII
 or US-ASCII compatible sets (for example the ISO-8859-x family, UTF-
 8, ISO-2022-xx, KOI8-R). If a non-US-ASCII compatible character set
 is used, appropriate code-point from that character set MUST be
 chosen instead. Use of non-US-ASCII-compatible character sets is NOT
 recommended.

3 Registration Information

 The Calendaring and Scheduling Core Object Specification is intended
 for use as a MIME content type. However, the implementation of the
 memo is in no way limited solely as a MIME content type.

3.1 Content Type

 The following text is intended to register this memo as the MIME
 content type "text/calendar".
   To: ietf-types@uninett.no
   Subject: Registration of MIME content type text/calendar.
   MIME media type name: text
   MIME subtype name: calendar

Dawson & Stenerson Standards Track [Page 8] RFC 2445 iCalendar November 1998

3.2 Parameters

 Required parameters: none
 Optional parameters: charset, method, component and optinfo
 The "charset" parameter is defined in [RFC 2046] for other body
 parts. It is used to identify the default character set used within
 the body part.
 The "method" parameter is used to convey the iCalendar object method
 or transaction semantics for the calendaring and scheduling
 information. It also is an identifier for the restricted set of
 properties and values that the iCalendar object consists of. The
 parameter is to be used as a guide for applications interpreting the
 information contained within the body part. It SHOULD NOT be used to
 exclude or require particular pieces of information unless the
 identified method definition specifically calls for this behavior.
 Unless specifically forbidden by a particular method definition, a
 text/calendar content type can contain any set of properties
 permitted by the Calendaring and Scheduling Core Object
 Specification. The "method" parameter MUST be the same value as that
 specified in the "METHOD" component property in the iCalendar object.
 If one is present, the other MUST also be present.
 The value for the "method" parameter is defined as follows:
      method  = 1*(ALPHA / DIGIT / "-")
      ; IANA registered iCalendar object method
 The "component" parameter conveys the type of iCalendar calendar
 component within the body part. If the iCalendar object contains more
 than one calendar component type, then multiple component parameters
 MUST be specified.
 The value for the "component" parameter is defined as follows:
      component       = ("VEVENT" / "VTODO" / "VJOURNAL" / "VFREEBUSY"
                      / "VTIMEZONE" / x-name / iana-token)
 The "optinfo" parameter conveys optional information about the
 iCalendar object within the body part. This parameter can only
 specify semantics already specified by the iCalendar object and that
 can be otherwise determined by parsing the body part. In addition,
 the optional information specified by this parameter MUST be
 consistent with that information specified by the iCalendar object.
 For example, it can be used to convey the "Attendee" response status
 to a meeting request. The parameter value consists of a string value.

Dawson & Stenerson Standards Track [Page 9] RFC 2445 iCalendar November 1998

 The parameter can be specified multiple times.
 This parameter MAY only specify semantics already specified by the
 iCalendar object and that can be otherwise determined by parsing the
 body part.
 The value for the "optinfo" parameter is defined as follows:
      optinfo = infovalue / qinfovalue
      infovalue       = iana-token / x-name
      qinfovalue      = DQUOTE (infovalue) DQUOTE

3.3 Content Header Fields

 Optional content header fields: Any header fields defined by [RFC
 2045].

3.4 Encoding Considerations

 This MIME content type can contain 8bit characters, so the use of
 quoted-printable or BASE64 MIME content-transfer-encodings might be
 necessary when iCalendar objects are transferred across protocols
 restricted to the 7bit repertoire. Note that a text valued property
 in the content entity can also have content encoding of special
 characters using a BACKSLASH character (US-ASCII decimal 92)
 escapement technique. This means that content values can end up
 encoded twice.

3.5 Security Considerations

 SPOOFING - - In this memo, the "Organizer" is the only person
 authorized to make changes to an existing "VEVENT", "VTODO",
 "VJOURNAL" calendar component and redistribute the updates to the
 "Attendees". An iCalendar object that maliciously changes or cancels
 an existing "VEVENT", "VTODO" or "VJOURNAL" or "VFREEBUSY" calendar
 component might be constructed by someone other than the "Organizer"
 and sent to the "Attendees". In addition in this memo, other than the
 "Organizer", an "Attendee" of a "VEVENT", "VTODO", "VJOURNAL"
 calendar component is the only other person authorized to update any
 parameter associated with their "ATTENDEE" property and send it to
 the "Organizer". An iCalendar object that maliciously changes the
 "ATTENDEE" parameters can be constructed by someone other than the
 real "Attendee" and sent to the "Organizer".

Dawson & Stenerson Standards Track [Page 10] RFC 2445 iCalendar November 1998

 PROCEDURAL ALARMS - - An iCalendar object can be created that
 contains a "VEVENT" and "VTODO" calendar component with "VALARM"
 calendar components. The "VALARM" calendar component can be of type
 PROCEDURE and can have an attachment containing some sort of
 executable program. Implementations that incorporate these types of
 alarms are subject to any virus or malicious attack that might occur
 as a result of executing the attachment.
 ATTACHMENTS - - An iCalendar object can include references to Uniform
 Resource Locators that can be programmed resources.
 Implementers and users of this memo should be aware of the network
 security implications of accepting and parsing such information. In
 addition, the security considerations observed by implementations of
 electronic mail systems should be followed for this memo.

3.6 Interoperability Considerations

 This MIME content type is intended to define a common format for
 conveying calendaring and scheduling information between different
 systems. It is heavily based on the earlier [VCAL] industry
 specification.

3.7 Applications Which Use This Media Type

 This content-type is designed for widespread use by Internet
 calendaring and scheduling applications. In addition, applications in
 the workflow and document management area might find this content-
 type applicable. The [ITIP] and [IMIP] Internet protocols directly
 use this content-type also. Future work on an Internet calendar
 access protocol will utilize this content-type too.

3.8 Additional Information

 This memo defines this content-type.

3.9 Magic Numbers

 None.

3.10 File Extensions

 The file extension of "ics" is to be used to designate a file
 containing (an arbitrary set of) calendaring and scheduling
 information consistent with this MIME content type.

Dawson & Stenerson Standards Track [Page 11] RFC 2445 iCalendar November 1998

 The file extension of "ifb" is to be used to designate a file
 containing free or busy time information consistent with this MIME
 content type.
 Macintosh file type codes: The file type code of "iCal" is to be used
 in Apple MacIntosh operating system environments to designate a file
 containing calendaring and scheduling information consistent with
 this MIME media type.
 The file type code of "iFBf" is to be used in Apple MacIntosh
 operating system environments to designate a file containing free or
 busy time information consistent with this MIME media type.

3.11 Contact for Further Information:

 Frank Dawson
 6544 Battleford Drive
 Raleigh, NC 27613-3502
 919-676-9515 (Telephone)
 919-676-9564 (Data/Facsimile)
 Frank_Dawson@Lotus.com (Internet Mail)
 Derik Stenerson
 One Microsoft Way
 Redmond, WA  98052-6399
 425-936-5522 (Telephone)
 425-936-7329 (Facsimile)
 deriks@microsoft.com (Internet Mail)

3.12 Intended Usage

 COMMON

3.13 Authors/Change Controllers

 Frank Dawson
 6544 Battleford Drive
 Raleigh, NC 27613-3502
 919-676-9515 (Telephone)
 919-676-9564 (Data/Facsimile)
 Frank_Dawson@Lotus.com (Internet Mail)
 Derik Stenerson
 One Microsoft Way
 Redmond, WA  98052-6399
 425-936-5522 (Telephone)
 425-936-7329 (Facsimile)
 deriks@microsoft.com (Internet Mail)

Dawson & Stenerson Standards Track [Page 12] RFC 2445 iCalendar November 1998

4 iCalendar Object Specification

 The following sections define the details of a Calendaring and
 Scheduling Core Object Specification. This information is intended to
 be an integral part of the MIME content type registration. In
 addition, this information can be used independent of such content
 registration. In particular, this memo has direct applicability for
 use as a calendaring and scheduling exchange format in file-, memory-
 or network-based transport mechanisms.

4.1 Content Lines

 The iCalendar object is organized into individual lines of text,
 called content lines. Content lines are delimited by a line break,
 which is a CRLF sequence (US-ASCII decimal 13, followed by US-ASCII
 decimal 10).
 Lines of text SHOULD NOT be longer than 75 octets, excluding the line
 break. Long content lines SHOULD be split into a multiple line
 representations using a line "folding" technique. That is, a long
 line can be split between any two characters by inserting a CRLF
 immediately followed by a single linear white space character (i.e.,
 SPACE, US-ASCII decimal 32 or HTAB, US-ASCII decimal 9). Any sequence
 of CRLF followed immediately by a single linear white space character
 is ignored (i.e., removed) when processing the content type.
 For example the line:
   DESCRIPTION:This is a long description that exists on a long line.
 Can be represented as:
   DESCRIPTION:This is a lo
    ng description
     that exists on a long line.
 The process of moving from this folded multiple line representation
 to its single line representation is called "unfolding". Unfolding is
 accomplished by removing the CRLF character and the linear white
 space character that immediately follows.
 When parsing a content line, folded lines MUST first be unfolded
 according to the unfolding procedure described above. When generating
 a content line, lines longer than 75 octets SHOULD be folded
 according to the folding procedure described above.

Dawson & Stenerson Standards Track [Page 13] RFC 2445 iCalendar November 1998

 The content information associated with an iCalendar object is
 formatted using a syntax similar to that defined by [RFC 2425]. That
 is, the content information consists of CRLF-separated content lines.
 The following notation defines the lines of content in an iCalendar
 object:
   contentline        = name *(";" param ) ":" value CRLF
      ; This ABNF is just a general definition for an initial parsing
      ; of the content line into its property name, parameter list,
      ; and value string
   ; When parsing a content line, folded lines MUST first
      ; be unfolded according to the unfolding procedure
      ; described above. When generating a content line, lines
      ; longer than 75 octets SHOULD be folded according to
      ; the folding procedure described above.
   name               = x-name / iana-token
   iana-token = 1*(ALPHA / DIGIT / "-")
   ; iCalendar identifier registered with IANA
   x-name             = "X-" [vendorid "-"] 1*(ALPHA / DIGIT / "-")
   ; Reservered for experimental use. Not intended for use in
   ; released products.
   vendorid   = 3*(ALPHA / DIGIT)     ;Vendor identification
   param              = param-name "=" param-value
                        *("," param-value)
      ; Each property defines the specific ABNF for the parameters
      ; allowed on the property. Refer to specific properties for
      ; precise parameter ABNF.
   param-name = iana-token / x-token
   param-value        = paramtext / quoted-string
   paramtext  = *SAFE-CHAR
   value      = *VALUE-CHAR
   quoted-string      = DQUOTE *QSAFE-CHAR DQUOTE
   NON-US-ASCII       = %x80-F8
   ; Use restricted by charset parameter
   ; on outer MIME object (UTF-8 preferred)

Dawson & Stenerson Standards Track [Page 14] RFC 2445 iCalendar November 1998

   QSAFE-CHAR = WSP / %x21 / %x23-7E / NON-US-ASCII
   ; Any character except CTLs and DQUOTE
   SAFE-CHAR  = WSP / %x21 / %x23-2B / %x2D-39 / %x3C-7E
              / NON-US-ASCII
   ; Any character except CTLs, DQUOTE, ";", ":", ","
   VALUE-CHAR = WSP / %x21-7E / NON-US-ASCII
   ; Any textual character
   CR = %x0D
   ; carriage return
   LF = %x0A
   ; line feed
   CRLF       = CR LF
   ; Internet standard newline
   CTL        = %x00-08 / %x0A-1F / %x7F
      ; Controls
   ALPHA      = %x41-5A / %x61-7A   ; A-Z / a-z
   DIGIT      = %x30-39
      ; 0-9
   DQUOTE     = %x22
      ; Quotation Mark
   WSP        = SPACE / HTAB
   SPACE      = %x20
   HTAB       = %x09
 The property value component of a content line has a format that is
 property specific. Refer to the section describing each property for
 a definition of this format.
 All names of properties, property parameters, enumerated property
 values and property parameter values are case-insensitive. However,
 all other property values are case-sensitive, unless otherwise
 stated.

Dawson & Stenerson Standards Track [Page 15] RFC 2445 iCalendar November 1998

4.1.1 List and Field Separators

 Some properties and parameters allow a list of values. Values in a
 list of values MUST be separated by a COMMA character (US-ASCII
 decimal 44). There is no significance to the order of values in a
 list. For those parameter values (such as those that specify URI
 values) that are specified in quoted-strings, the individual quoted-
 strings are separated by a COMMA character (US-ASCII decimal 44).
 Some property values are defined in terms of multiple parts. These
 structured property values MUST have their value parts separated by a
 SEMICOLON character (US-ASCII decimal 59).
 Some properties allow a list of parameters. Each property parameter
 in a list of property parameters MUST be separated by a SEMICOLON
 character (US-ASCII decimal 59).
 Property parameters with values containing a COLON, a SEMICOLON or a
 COMMA character MUST be placed in quoted text.
 For example, in the following properties a SEMICOLON is used to
 separate property parameters from each other, and a COMMA is used to
 separate property values in a value list.
   ATTENDEE;RSVP=TRUE;ROLE=REQ-PARTICIPANT:MAILTO:
    jsmith@host.com
   RDATE;VALUE=DATE:19970304,19970504,19970704,19970904

4.1.2 Multiple Values

 Some properties defined in the iCalendar object can have multiple
 values. The general rule for encoding multi-valued items is to simply
 create a new content line for each value, including the property
 name. However, it should be noted that some properties support
 encoding multiple values in a single property by separating the
 values with a COMMA character (US-ASCII decimal 44). Individual
 property definitions should be consulted for determining whether a
 specific property allows multiple values and in which of these two
 forms.

4.1.3 Binary Content

 Binary content information in an iCalendar object SHOULD be
 referenced using a URI within a property value. That is the binary
 content information SHOULD be placed in an external MIME entity that
 can be referenced by a URI from within the iCalendar object. In
 applications where this is not feasible, binary content information

Dawson & Stenerson Standards Track [Page 16] RFC 2445 iCalendar November 1998

 can be included within an iCalendar object, but only after first
 encoding it into text using the "BASE64" encoding method defined in
 [RFC 2045]. Inline binary contact SHOULD only be used in applications
 whose special circumstances demand that an iCalendar object be
 expressed as a single entity. A property containing inline binary
 content information MUST specify the "ENCODING" property parameter.
 Binary content information placed external to the iCalendar object
 MUST be referenced by a uniform resource identifier (URI).
 The following example specifies an "ATTACH" property that references
 an attachment external to the iCalendar object with a URI reference:
   ATTACH:http://xyz.com/public/quarterly-report.doc
 The following example specifies an "ATTACH" property with inline
 binary encoded content information:
   ATTACH;FMTTYPE=image/basic;ENCODING=BASE64;VALUE=BINARY:
    MIICajCCAdOgAwIBAgICBEUwDQYJKoZIhvcNAQEEBQAwdzELMAkGA1U
    EBhMCVVMxLDAqBgNVBAoTI05ldHNjYXBlIENvbW11bmljYXRpb25zIE
      <...remainder of "BASE64" encoded binary data...>

4.1.4 Character Set

 There is not a property parameter to declare the character set used
 in a property value. The default character set for an iCalendar
 object is UTF-8 as defined in [RFC 2279].
 The "charset" Content-Type parameter can be used in MIME transports
 to specify any other IANA registered character set.

4.2 Property Parameters

 A property can have attributes associated with it. These "property
 parameters" contain meta-information about the property or the
 property value. Property parameters are provided to specify such
 information as the location of an alternate text representation for a
 property value, the language of a text property value, the data type
 of the property value and other attributes.
 Property parameter values that contain the COLON (US-ASCII decimal
 58), SEMICOLON (US-ASCII decimal 59) or COMMA (US-ASCII decimal 44)
 character separators MUST be specified as quoted-string text values.
 Property parameter values MUST NOT contain the DOUBLE-QUOTE (US-ASCII
 decimal 22) character. The DOUBLE-QUOTE (US-ASCII decimal 22)
 character is used as a delimiter for parameter values that contain
 restricted characters or URI text. For example:

Dawson & Stenerson Standards Track [Page 17] RFC 2445 iCalendar November 1998

   DESCRIPTION;ALTREP="http://www.wiz.org":The Fall'98 Wild Wizards
     Conference - - Las Vegas, NV, USA
 Property parameter values that are not in quoted strings are case
 insensitive.
 The general property parameters defined by this memo are defined by
 the following notation:
   parameter  = altrepparam           ; Alternate text representation
              / cnparam               ; Common name
              / cutypeparam           ; Calendar user type
              / delfromparam          ; Delegator
              / deltoparam            ; Delegatee
              / dirparam              ; Directory entry
              / encodingparam         ; Inline encoding
              / fmttypeparam          ; Format type
              / fbtypeparam           ; Free/busy time type
              / languageparam         ; Language for text
              / memberparam           ; Group or list membership
              / partstatparam         ; Participation status
              / rangeparam            ; Recurrence identifier range
              / trigrelparam          ; Alarm trigger relationship
              / reltypeparam          ; Relationship type
              / roleparam             ; Participation role
              / rsvpparam             ; RSVP expectation
              / sentbyparam           ; Sent by
              / tzidparam             ; Reference to time zone object
              / valuetypeparam        ; Property value data type
              / ianaparam
      ; Some other IANA registered iCalendar parameter.
              / xparam
      ; A non-standard, experimental parameter.
   ianaparam  = iana-token "=" param-value *("," param-value)
   xparam     =x-name "=" param-value *("," param-value)

4.2.1 Alternate Text Representation

 Parameter Name: ALTREP
 Purpose: To specify an alternate text representation for the property
 value.
 Format Definition: The property parameter is defined by the following
 notation:

Dawson & Stenerson Standards Track [Page 18] RFC 2445 iCalendar November 1998

   altrepparam        = "ALTREP" "=" DQUOTE uri DQUOTE
 Description: The parameter specifies a URI that points to an
 alternate representation for a textual property value. A property
 specifying this parameter MUST also include a value that reflects the
 default representation of the text value. The individual URI
 parameter values MUST each be specified in a quoted-string.
 Example:
   DESCRIPTION;ALTREP="CID:<part3.msg.970415T083000@host.com>":Project
     XYZ Review Meeting will include the following agenda items: (a)
     Market Overview, (b) Finances, (c) Project Management
 The "ALTREP" property parameter value might point to a "text/html"
 content portion.
   Content-Type:text/html
   Content-Id:<part3.msg.970415T083000@host.com>
   <html><body>
   <p><b>Project XYZ Review Meeting</b> will include the following
   agenda items:<ol><li>Market
   Overview</li><li>Finances</li><li>Project Management</li></ol></p>
   </body></html>

4.2.2 Common Name

 Parameter Name: CN
 Purpose: To specify the common name to be associated with the
 calendar user specified by the property.
 Format Definition: The property parameter is defined by the following
 notation:
   cnparam    = "CN" "=" param-value
 Description: This parameter can be specified on properties with a
 CAL-ADDRESS value type. The parameter specifies the common name to be
 associated with the calendar user specified by the property. The
 parameter value is text. The parameter value can be used for display
 text to be associated with the calendar address specified by the
 property.

Dawson & Stenerson Standards Track [Page 19] RFC 2445 iCalendar November 1998

 Example:
   ORGANIZER;CN="John Smith":MAILTO:jsmith@host.com

4.2.3 Calendar User Type

 Parameter Name: CUTYPE
 Purpose: To specify the type of calendar user specified by the
 property.
 Format Definition: The property parameter is defined by the following
 notation:
   cutypeparam        = "CUTYPE" "="
                       ("INDIVIDUAL"          ; An individual
                      / "GROUP"               ; A group of individuals
                      / "RESOURCE"            ; A physical resource
                      / "ROOM"                ; A room resource
                      / "UNKNOWN"             ; Otherwise not known
                      / x-name                ; Experimental type
                      / iana-token)           ; Other IANA registered
                                              ; type
   ; Default is INDIVIDUAL
 Description: This parameter can be specified on properties with a
 CAL-ADDRESS value type. The parameter identifies the type of calendar
 user specified by the property. If not specified on a property that
 allows this parameter, the default is INDIVIDUAL.
 Example:
   ATTENDEE;CUTYPE=GROUP:MAILTO:ietf-calsch@imc.org

4.2.4 Delegators

 Parameter Name: DELEGATED-FROM
 Purpose: To specify the calendar users that have delegated their
 participation to the calendar user specified by the property.
 Format Definition: The property parameter is defined by the following
 notation:
   delfromparam       = "DELEGATED-FROM" "=" DQUOTE cal-address DQUOTE
                        *("," DQUOTE cal-address DQUOTE)

Dawson & Stenerson Standards Track [Page 20] RFC 2445 iCalendar November 1998

 Description: This parameter can be specified on properties with a
 CAL-ADDRESS value type. This parameter can be specified on a property
 that has a value type of calendar address. This parameter specifies
 those calendar uses that have delegated their participation in a
 group scheduled event or to-do to the calendar user specified by the
 property. The value MUST be a MAILTO URI as defined in [RFC 1738].
 The individual calendar address parameter values MUST each be
 specified in a quoted-string.
 Example:
   ATTENDEE;DELEGATED-FROM="MAILTO:jsmith@host.com":MAILTO:
    jdoe@host.com

4.2.5 Delegatees

 Parameter Name: DELEGATED-TO
 Purpose: To specify the calendar users to whom the calendar user
 specified by the property has delegated participation.
 Format Definition: The property parameter is defined by the following
 notation:
   deltoparam = "DELEGATED-TO" "=" DQUOTE cal-address DQUOTE
                *("," DQUOTE cal-address DQUOTE)
 Description: This parameter can be specified on properties with a
 CAL-ADDRESS value type. This parameter specifies those calendar users
 whom have been delegated participation in a group scheduled event or
 to-do by the calendar user specified by the property. The value MUST
 be a MAILTO URI as defined in [RFC 1738]. The individual calendar
 address parameter values MUST each be specified in a quoted-string.
 Example:
   ATTENDEE;DELEGATED-TO="MAILTO:jdoe@host.com","MAILTO:jqpublic@
    host.com":MAILTO:jsmith@host.com

4.2.6 Directory Entry Reference

 Parameter Name: DIR
 Purpose: To specify reference to a directory entry associated with
 the calendar user specified by the property.
 Format Definition: The property parameter is defined by the following
 notation:

Dawson & Stenerson Standards Track [Page 21] RFC 2445 iCalendar November 1998

   dirparam   = "DIR" "=" DQUOTE uri DQUOTE
 Description: This parameter can be specified on properties with a
 CAL-ADDRESS value type. The parameter specifies a reference to the
 directory entry associated with the calendar user specified by the
 property. The parameter value is a URI. The individual URI parameter
 values MUST each be specified in a quoted-string.
 Example:
   ORGANIZER;DIR="ldap://host.com:6666/o=eDABC%20Industries,c=3DUS??
    (cn=3DBJim%20Dolittle)":MAILTO:jimdo@host1.com

4.2.7 Inline Encoding

 Parameter Name: ENCODING
 Purpose: To specify an alternate inline encoding for the property
 value.
 Format Definition: The property parameter is defined by the following
 notation:
   encodingparam      = "ENCODING" "="
                        ("8BIT"
      ; "8bit" text encoding is defined in [RFC 2045]
                      / "BASE64"
      ; "BASE64" binary encoding format is defined in [RFC 2045]
                      / iana-token
      ; Some other IANA registered iCalendar encoding type
                      / x-name)
      ; A non-standard, experimental encoding type
 Description: The property parameter identifies the inline encoding
 used in a property value. The default encoding is "8BIT",
 corresponding to a property value consisting of text. The "BASE64"
 encoding type corresponds to a property value encoded using the
 "BASE64" encoding defined in [RFC 2045].
 If the value type parameter is ";VALUE=BINARY", then the inline
 encoding parameter MUST be specified with the value
 ";ENCODING=BASE64".

Dawson & Stenerson Standards Track [Page 22] RFC 2445 iCalendar November 1998

 Example:
   ATTACH;FMTYPE=IMAGE/JPEG;ENCODING=BASE64;VALUE=BINARY:MIICajC
    CAdOgAwIBAgICBEUwDQYJKoZIhvcNAQEEBQAwdzELMAkGA1UEBhMCVVMxLDA
    qBgNVBAoTI05ldHNjYXBlIENvbW11bmljYXRpb25zIENvcnBvcmF0aW9uMRw
    <...remainder of "BASE64" encoded binary data...>

4.2.8 Format Type

 Parameter Name: FMTTYPE
 Purpose: To specify the content type of a referenced object.
 Format Definition: The property parameter is defined by the following
 notation:
   fmttypeparam       = "FMTTYPE" "=" iana-token
                                      ; A IANA registered content type
                                   / x-name
                                      ; A non-standard content type
 Description: This parameter can be specified on properties that are
 used to reference an object. The parameter specifies the content type
 of the referenced object. For example, on the "ATTACH" property, a
 FTP type URI value does not, by itself, necessarily convey the type
 of content associated with the resource. The parameter value MUST be
 the TEXT for either an IANA registered content type or a non-standard
 content type.
   Example:
    ATTACH;FMTTYPE=application/binary:ftp://domain.com/pub/docs/
     agenda.doc

4.2.9 Free/Busy Time Type

 Parameter Name: FBTYPE
 Purpose: To specify the free or busy time type.
 Format Definition: The property parameter is defined by the following
 notation:
   fbtypeparam        = "FBTYPE" "=" ("FREE" / "BUSY"
                      / "BUSY-UNAVAILABLE" / "BUSY-TENTATIVE"
                      / x-name
      ; Some experimental iCalendar data type.
                      / iana-token)

Dawson & Stenerson Standards Track [Page 23] RFC 2445 iCalendar November 1998

      ; Some other IANA registered iCalendar data type.
 Description: The parameter specifies the free or busy time type. The
 value FREE indicates that the time interval is free for scheduling.
 The value BUSY indicates that the time interval is busy because one
 or more events have been scheduled for that interval. The value
 BUSY-UNAVAILABLE indicates that the time interval is busy and that
 the interval can not be scheduled. The value BUSY-TENTATIVE indicates
 that the time interval is busy because one or more events have been
 tentatively scheduled for that interval. If not specified on a
 property that allows this parameter, the default is BUSY.
 Example: The following is an example of this parameter on a FREEBUSY
 property.
   FREEBUSY;FBTYPE=BUSY:19980415T133000Z/19980415T170000Z

4.2.10 Language

 Parameter Name: LANGUAGE
 Purpose: To specify the language for text values in a property or
 property parameter.
 Format Definition: The property parameter is defined by the following
 notation:
   languageparam =    "LANGUAGE" "=" language
   language = <Text identifying a language, as defined in [RFC 1766]>
 Description: This parameter can be specified on properties with a
 text value type. The parameter identifies the language of the text in
 the property or property parameter value. The value of the "language"
 property parameter is that defined in [RFC 1766].
 For transport in a MIME entity, the Content-Language header field can
 be used to set the default language for the entire body part.
 Otherwise, no default language is assumed.
 Example:
   SUMMARY;LANGUAGE=us-EN:Company Holiday Party
   LOCATION;LANGUAGE=en:Germany
   LOCATION;LANGUAGE=no:Tyskland

Dawson & Stenerson Standards Track [Page 24] RFC 2445 iCalendar November 1998

 The following example makes use of the Quoted-Printable encoding in
 order to represent non-ASCII characters.
   LOCATION;LANGUAGE=da:K=F8benhavn
   LOCATION;LANGUAGE=en:Copenhagen

4.2.11 Group or List Membership

 Parameter Name: MEMBER
 Purpose: To specify the group or list membership of the calendar user
 specified by the property.
 Format Definition: The property parameter is defined by the following
 notation:
   memberparam        = "MEMBER" "=" DQUOTE cal-address DQUOTE
                        *("," DQUOTE cal-address DQUOTE)
 Description: This parameter can be specified on properties with a
 CAL-ADDRESS value type. The parameter identifies the groups or list
 membership for the calendar user specified by the property. The
 parameter value either a single calendar address in a quoted-string
 or a COMMA character (US-ASCII decimal 44) list of calendar
 addresses, each in a quoted-string. The individual calendar address
 parameter values MUST each be specified in a quoted-string.
 Example:
   ATTENDEE;MEMBER="MAILTO:ietf-calsch@imc.org":MAILTO:jsmith@host.com
   ATTENDEE;MEMBER="MAILTO:projectA@host.com","MAILTO:projectB@host.
    com":MAILTO:janedoe@host.com

4.2.12 Participation Status

 Parameter Name: PARTSTAT
 Purpose: To specify the participation status for the calendar user
 specified by the property.
 Format Definition: The property parameter is defined by the following
 notation:
   partstatparam      = "PARTSTAT" "="
                       ("NEEDS-ACTION"        ; Event needs action
                      / "ACCEPTED"            ; Event accepted
                      / "DECLINED"            ; Event declined

Dawson & Stenerson Standards Track [Page 25] RFC 2445 iCalendar November 1998

                      / "TENTATIVE"           ; Event tentatively
                                              ; accepted
                      / "DELEGATED"           ; Event delegated
                      / x-name                ; Experimental status
                      / iana-token)           ; Other IANA registered
                                              ; status
   ; These are the participation statuses for a "VEVENT". Default is
   ; NEEDS-ACTION
   partstatparam      /= "PARTSTAT" "="
                       ("NEEDS-ACTION"        ; To-do needs action
                      / "ACCEPTED"            ; To-do accepted
                      / "DECLINED"            ; To-do declined
                      / "TENTATIVE"           ; To-do tentatively
                                              ; accepted
                      / "DELEGATED"           ; To-do delegated
                      / "COMPLETED"           ; To-do completed.
                                              ; COMPLETED property has
                                              ;date/time completed.
                      / "IN-PROCESS"          ; To-do in process of
                                              ; being completed
                      / x-name                ; Experimental status
                      / iana-token)           ; Other IANA registered
                                              ; status
   ; These are the participation statuses for a "VTODO". Default is
   ; NEEDS-ACTION
   partstatparam      /= "PARTSTAT" "="
                       ("NEEDS-ACTION"        ; Journal needs action
                      / "ACCEPTED"            ; Journal accepted
                      / "DECLINED"            ; Journal declined
                      / x-name                ; Experimental status
                      / iana-token)           ; Other IANA registered
                                              ; status
   ; These are the participation statuses for a "VJOURNAL". Default is
   ; NEEDS-ACTION
 Description: This parameter can be specified on properties with a
 CAL-ADDRESS value type. The parameter identifies the participation
 status for the calendar user specified by the property value. The
 parameter values differ depending on whether they are associated with
 a group scheduled "VEVENT", "VTODO" or "VJOURNAL". The values MUST
 match one of the values allowed for the given calendar component. If
 not specified on a property that allows this parameter, the default
 value is NEEDS-ACTION.
 Example:
   ATTENDEE;PARTSTAT=DECLINED:MAILTO:jsmith@host.com

Dawson & Stenerson Standards Track [Page 26] RFC 2445 iCalendar November 1998

4.2.13 Recurrence Identifier Range

 Parameter Name: RANGE
 Purpose: To specify the effective range of recurrence instances from
 the instance specified by the recurrence identifier specified by the
 property.
 Format Definition: The property parameter is defined by the following
 notation:
   rangeparam = "RANGE" "=" ("THISANDPRIOR"
      ; To specify all instances prior to the recurrence identifier
              / "THISANDFUTURE")
      ; To specify the instance specified by the recurrence identifier
      ; and all subsequent recurrence instances
 Description: The parameter can be specified on a property that
 specifies a recurrence identifier. The parameter specifies the
 effective range of recurrence instances that is specified by the
 property. The effective range is from the recurrence identified
 specified by the property. If this parameter is not specified an
 allowed property, then the default range is the single instance
 specified by the recurrence identifier value of the property. The
 parameter value can be "THISANDPRIOR" to indicate a range defined by
 the recurrence identified value of the property and all prior
 instances. The parameter value can also be "THISANDFUTURE" to
 indicate a range defined by the recurrence identifier and all
 subsequent instances.
 Example:
   RECURRENCE-ID;RANGE=THISANDPRIOR:19980401T133000Z

4.2.14 Alarm Trigger Relationship

 Parameter Name: RELATED
 Purpose: To specify the relationship of the alarm trigger with
 respect to the start or end of the calendar component.
 Format Definition: The property parameter is defined by the following
 notation:
   trigrelparam       = "RELATED" "="
                       ("START"       ; Trigger off of start
                      / "END")        ; Trigger off of end

Dawson & Stenerson Standards Track [Page 27] RFC 2445 iCalendar November 1998

 Description: The parameter can be specified on properties that
 specify an alarm trigger with a DURATION value type. The parameter
 specifies whether the alarm will trigger relative to the start or end
 of the calendar component. The parameter value START will set the
 alarm to trigger off the start of the calendar component; the
 parameter value END will set the alarm to trigger off the end of the
 calendar component. If the parameter is not specified on an allowable
 property, then the default is START.
 Example:
   TRIGGER;RELATED=END:PT5M

4.2.15 Relationship Type

 Parameter Name: RELTYPE
 Purpose: To specify the type of hierarchical relationship associated
 with the calendar component specified by the property.
 Format Definition: The property parameter is defined by the following
 notation:
   reltypeparam       = "RELTYPE" "="
                       ("PARENT"      ; Parent relationship. Default.
                      / "CHILD"       ; Child relationship
                      / "SIBLING      ; Sibling relationship
                      / iana-token    ; Some other IANA registered
                                      ; iCalendar relationship type
                      / x-name)       ; A non-standard, experimental
                                      ; relationship type
 Description: This parameter can be specified on a property that
 references another related calendar. The parameter specifies the
 hierarchical relationship type of the calendar component referenced
 by the property. The parameter value can be PARENT, to indicate that
 the referenced calendar component is a superior of calendar
 component; CHILD to indicate that the referenced calendar component
 is a subordinate of the calendar component; SIBLING to indicate that
 the referenced calendar component is a peer of the calendar
 component. If this parameter is not specified on an allowable
 property, the default relationship type is PARENT.
 Example:
   RELATED-TO;RELTYPE=SIBLING:<19960401-080045-4000F192713@host.com>

Dawson & Stenerson Standards Track [Page 28] RFC 2445 iCalendar November 1998

4.2.16 Participation Role

 Parameter Name: ROLE
 Purpose: To specify the participation role for the calendar user
 specified by the property.
 Format Definition: The property parameter is defined by the following
 notation:
   roleparam  = "ROLE" "="
               ("CHAIR"               ; Indicates chair of the
                                      ; calendar entity
              / "REQ-PARTICIPANT"     ; Indicates a participant whose
                                      ; participation is required
              / "OPT-PARTICIPANT"     ; Indicates a participant whose
                                      ; participation is optional
              / "NON-PARTICIPANT"     ; Indicates a participant who is
                                      ; copied for information
                                      ; purposes only
              / x-name                ; Experimental role
              / iana-token)           ; Other IANA role
   ; Default is REQ-PARTICIPANT
 Description: This parameter can be specified on properties with a
 CAL-ADDRESS value type. The parameter specifies the participation
 role for the calendar user specified by the property in the group
 schedule calendar component. If not specified on a property that
 allows this parameter, the default value is REQ-PARTICIPANT.
 Example:
   ATTENDEE;ROLE=CHAIR:MAILTO:mrbig@host.com

4.2.17 RSVP Expectation

 Parameter Name: RSVP
 Purpose: To specify whether there is an expectation of a favor of a
 reply from the calendar user specified by the property value.
 Format Definition: The property parameter is defined by the following
 notation:
   rsvpparam = "RSVP" "=" ("TRUE" / "FALSE")
   ; Default is FALSE

Dawson & Stenerson Standards Track [Page 29] RFC 2445 iCalendar November 1998

 Description: This parameter can be specified on properties with a
 CAL-ADDRESS value type. The parameter identifies the expectation of a
 reply from the calendar user specified by the property value. This
 parameter is used by the "Organizer" to request a participation
 status reply from an "Attendee" of a group scheduled event or to-do.
 If not specified on a property that allows this parameter, the
 default value is FALSE.
 Example:
   ATTENDEE;RSVP=TRUE:MAILTO:jsmith@host.com

4.2.18 Sent By

 Parameter Name: SENT-BY
 Purpose: To specify the calendar user that is acting on behalf of the
 calendar user specified by the property.
 Format Definition: The property parameter is defined by the following
 notation:
   sentbyparam        = "SENT-BY" "=" DQUOTE cal-address DQUOTE
 Description: This parameter can be specified on properties with a
 CAL-ADDRESS value type. The parameter specifies the calendar user
 that is acting on behalf of the calendar user specified by the
 property. The parameter value MUST be a MAILTO URI as defined in [RFC
 1738]. The individual calendar address parameter values MUST each be
 specified in a quoted-string.
 Example:
   ORGANIZER;SENT-BY:"MAILTO:sray@host.com":MAILTO:jsmith@host.com

4.2.19 Time Zone Identifier

 Parameter Name: TZID
 Purpose: To specify the identifier for the time zone definition for a
 time component in the property value.
 Format Definition: This property parameter is defined by the
 following notation:
   tzidparam  = "TZID" "=" [tzidprefix] paramtext CRLF
   tzidprefix = "/"

Dawson & Stenerson Standards Track [Page 30] RFC 2445 iCalendar November 1998

 Description: The parameter MUST be specified on the "DTSTART",
 "DTEND", "DUE", "EXDATE" and "RDATE" properties when either a DATE-
 TIME or TIME value type is specified and when the value is not either
 a UTC or a "floating" time. Refer to the DATE-TIME or TIME value type
 definition for a description of UTC and "floating time" formats. This
 property parameter specifies a text value which uniquely identifies
 the "VTIMEZONE" calendar component to be used when evaluating the
 time portion of the property. The value of the TZID property
 parameter will be equal to the value of the TZID property for the
 matching time zone definition. An individual "VTIMEZONE" calendar
 component MUST be specified for each unique "TZID" parameter value
 specified in the iCalendar object.
 The parameter MUST be specified on properties with a DATE-TIME value
 if the DATE-TIME is not either a UTC or a "floating" time.
 The presence of the SOLIDUS character (US-ASCII decimal 47) as a
 prefix, indicates that this TZID represents a unique ID in a globally
 defined time zone registry (when such registry is defined).
      Note: This document does not define a naming convention for time
      zone identifiers. Implementers may want to use the naming
      conventions defined in existing time zone specifications such as
      the public-domain Olson database [TZ]. The specification of
      globally unique time zone identifiers is not addressed by this
      document and is left for future study.
 The following are examples of this property parameter:
   DTSTART;TZID=US-Eastern:19980119T020000
   DTEND;TZID=US-Eastern:19980119T030000
 The TZID property parameter MUST NOT be applied to DATE-TIME or TIME
 properties whose time values are specified in UTC.
 The use of local time in a DATE-TIME or TIME value without the TZID
 property parameter is to be interpreted as a local time value,
 regardless of the existence of "VTIMEZONE" calendar components in the
 iCalendar object.
 For more information see the sections on the data types DATE-TIME and
 TIME.

Dawson & Stenerson Standards Track [Page 31] RFC 2445 iCalendar November 1998

4.2.20 Value Data Types

 Parameter Name: VALUE
 Purpose: To explicitly specify the data type format for a property
 value.
 Format Definition: The "VALUE" property parameter is defined by the
 following notation:
   valuetypeparam = "VALUE" "=" valuetype
   valuetype  = ("BINARY"
              / "BOOLEAN"
              / "CAL-ADDRESS"
              / "DATE"
              / "DATE-TIME"
              / "DURATION"
              / "FLOAT"
              / "INTEGER"
              / "PERIOD"
              / "RECUR"
              / "TEXT"
              / "TIME"
              / "URI"
              / "UTC-OFFSET"
              / x-name
              ; Some experimental iCalendar data type.
              / iana-token)
              ; Some other IANA registered iCalendar data type.
 Description: The parameter specifies the data type and format of the
 property value. The property values MUST be of a single value type.
 For example, a "RDATE" property cannot have a combination of DATE-
 TIME and TIME value types.
 If the property's value is the default value type, then this
 parameter need not be specified. However, if the property's default
 value type is overridden by some other allowable value type, then
 this parameter MUST be specified.

4.3 Property Value Data Types

 The properties in an iCalendar object are strongly typed. The
 definition of each property restricts the value to be one of the
 value data types, or simply value types, defined in this section. The
 value type for a property will either be specified implicitly as the
 default value type or will be explicitly specified with the "VALUE"

Dawson & Stenerson Standards Track [Page 32] RFC 2445 iCalendar November 1998

 parameter. If the value type of a property is one of the alternate
 valid types, then it MUST be explicitly specified with the "VALUE"
 parameter.

4.3.1 Binary

 Value Name: BINARY
 Purpose: This value type is used to identify properties that contain
 a character encoding of inline binary data. For example, an inline
 attachment of an object code might be included in an iCalendar
 object.
 Formal Definition: The value type is defined by the following
 notation:
   binary     = *(4b-char) [b-end]
   ; A "BASE64" encoded character string, as defined by [RFC 2045].
   b-end      = (2b-char "==") / (3b-char "=")
   b-char = ALPHA / DIGIT / "+" / "/"
 Description: Property values with this value type MUST also include
 the inline encoding parameter sequence of ";ENCODING=BASE64". That
 is, all inline binary data MUST first be character encoded using the
 "BASE64" encoding method defined in [RFC 2045]. No additional content
 value encoding (i.e., BACKSLASH character encoding) is defined for
 this value type.
 Example: The following is an abridged example of a "BASE64" encoded
 binary value data.
   ATTACH;VALUE=BINARY;ENCODING=BASE64:MIICajCCAdOgAwIBAgICBEUwDQY
    JKoZIhvcNAQEEBQAwdzELMAkGA1UEBhMCVVMxLDAqBgNVBAoTI05ldHNjYXBlI
    ENvbW11bmljYXRpb25zIENvcnBvcmF0aW9uMRwwGgYDVQQLExNJbmZv
      <...remainder of "BASE64" encoded binary data...>

4.3.2 Boolean

 Value Name: BOOLEAN
 Purpose: This value type is used to identify properties that contain
 either a "TRUE" or "FALSE" Boolean value.
 Formal Definition: The value type is defined by the following
 notation:

Dawson & Stenerson Standards Track [Page 33] RFC 2445 iCalendar November 1998

   boolean    = "TRUE" / "FALSE"
 Description: These values are case insensitive text. No additional
 content value encoding (i.e., BACKSLASH character encoding) is
 defined for this value type.
 Example: The following is an example of a hypothetical property that
 has a BOOLEAN value type:
 GIBBERISH:TRUE

4.3.3 Calendar User Address

 Value Name: CAL-ADDRESS
 Purpose: This value type is used to identify properties that contain
 a calendar user address.
 Formal Definition: The value type is as defined by the following
 notation:
   cal-address        = uri
 Description: The value is a URI as defined by [RFC 1738] or any other
 IANA registered form for a URI. When used to address an Internet
 email transport address for a calendar user, the value MUST be a
 MAILTO URI, as defined by [RFC 1738]. No additional content value
 encoding (i.e., BACKSLASH character encoding) is defined for this
 value type.
 Example:
   ATTENDEE:MAILTO:jane_doe@host.com

4.3.4 Date

 Value Name: DATE
 Purpose: This value type is used to identify values that contain a
 calendar date.
 Formal Definition: The value type is defined by the following
 notation:
   date               = date-value
   date-value         = date-fullyear date-month date-mday
   date-fullyear      = 4DIGIT

Dawson & Stenerson Standards Track [Page 34] RFC 2445 iCalendar November 1998

   date-month         = 2DIGIT        ;01-12
   date-mday          = 2DIGIT        ;01-28, 01-29, 01-30, 01-31
                                      ;based on month/year
 Description: If the property permits, multiple "date" values are
 specified as a COMMA character (US-ASCII decimal 44) separated list
 of values. The format for the value type is expressed as the [ISO
 8601] complete representation, basic format for a calendar date. The
 textual format specifies a four-digit year, two-digit month, and
 two-digit day of the month. There are no separator characters between
 the year, month and day component text.
 No additional content value encoding (i.e., BACKSLASH character
 encoding) is defined for this value type.
 Example: The following represents July 14, 1997:
   19970714

4.3.5 Date-Time

 Value Name: DATE-TIME
 Purpose: This value type is used to identify values that specify a
 precise calendar date and time of day.
 Formal Definition: The value type is defined by the following
 notation:
   date-time  = date "T" time ;As specified in the date and time
                              ;value definitions
 Description: If the property permits, multiple "date-time" values are
 specified as a COMMA character (US-ASCII decimal 44) separated list
 of values. No additional content value encoding (i.e., BACKSLASH
 character encoding) is defined for this value type.
 The "DATE-TIME" data type is used to identify values that contain a
 precise calendar date and time of day. The format is based on the
 [ISO 8601] complete representation, basic format for a calendar date
 and time of day. The text format is a concatenation of the "date",
 followed by the LATIN CAPITAL LETTER T character (US-ASCII decimal
 84) time designator, followed by the "time" format.
 The "DATE-TIME" data type expresses time values in three forms:
 The form of date and time with UTC offset MUST NOT be used. For
 example, the following is not valid for a date-time value:

Dawson & Stenerson Standards Track [Page 35] RFC 2445 iCalendar November 1998

   DTSTART:19980119T230000-0800       ;Invalid time format
 FORM #1: DATE WITH LOCAL TIME
 The date with local time form is simply a date-time value that does
 not contain the UTC designator nor does it reference a time zone. For
 example, the following represents Janurary 18, 1998, at 11 PM:
   DTSTART:19980118T230000
 Date-time values of this type are said to be "floating" and are not
 bound to any time zone in particular. They are used to represent the
 same hour, minute, and second value regardless of which time zone is
 currently being observed. For example, an event can be defined that
 indicates that an individual will be busy from 11:00 AM to 1:00 PM
 every day, no matter which time zone the person is in. In these
 cases, a local time can be specified. The recipient of an iCalendar
 object with a property value consisting of a local time, without any
 relative time zone information, SHOULD interpret the value as being
 fixed to whatever time zone the ATTENDEE is in at any given moment.
 This means that two ATTENDEEs, in different time zones, receiving the
 same event definition as a floating time, may be participating in the
 event at different actual times. Floating time SHOULD only be used
 where that is the reasonable behavior.
 In most cases, a fixed time is desired. To properly communicate a
 fixed time in a property value, either UTC time or local time with
 time zone reference MUST be specified.
 The use of local time in a DATE-TIME value without the TZID property
 parameter is to be interpreted as floating time, regardless of the
 existence of "VTIMEZONE" calendar components in the iCalendar object.
 FORM #2: DATE WITH UTC TIME
 The date with UTC time, or absolute time, is identified by a LATIN
 CAPITAL LETTER Z suffix character (US-ASCII decimal 90), the UTC
 designator, appended to the time value. For example, the following
 represents January 19, 1998, at 0700 UTC:
   DTSTART:19980119T070000Z
 The TZID property parameter MUST NOT be applied to DATE-TIME
 properties whose time values are specified in UTC.
 FORM #3: DATE WITH LOCAL TIME AND TIME ZONE REFERENCE

Dawson & Stenerson Standards Track [Page 36] RFC 2445 iCalendar November 1998

 The date and local time with reference to time zone information is
 identified by the use the TZID property parameter to reference the
 appropriate time zone definition. TZID is discussed in detail in the
 section on Time Zone. For example, the following represents 2 AM in
 New York on Janurary 19, 1998:
        DTSTART;TZID=US-Eastern:19980119T020000
 Example: The following represents July 14, 1997, at 1:30 PM in New
 York City in each of the three time formats, using the "DTSTART"
 property.
   DTSTART:19970714T133000            ;Local time
   DTSTART:19970714T173000Z           ;UTC time
   DTSTART;TZID=US-Eastern:19970714T133000    ;Local time and time
                      ; zone reference
 A time value MUST ONLY specify 60 seconds when specifying the
 periodic "leap second" in the time value. For example:
   COMPLETED:19970630T235960Z

4.3.6 Duration

 Value Name: DURATION
 Purpose: This value type is used to identify properties that contain
 a duration of time.
 Formal Definition: The value type is defined by the following
 notation:
   dur-value  = (["+"] / "-") "P" (dur-date / dur-time / dur-week)
   dur-date   = dur-day [dur-time]
   dur-time   = "T" (dur-hour / dur-minute / dur-second)
   dur-week   = 1*DIGIT "W"
   dur-hour   = 1*DIGIT "H" [dur-minute]
   dur-minute = 1*DIGIT "M" [dur-second]
   dur-second = 1*DIGIT "S"
   dur-day    = 1*DIGIT "D"
 Description: If the property permits, multiple "duration" values are
 specified by a COMMA character (US-ASCII decimal 44) separated list
 of values. The format is expressed as the [ISO 8601] basic format for
 the duration of time. The format can represent durations in terms of
 weeks, days, hours, minutes, and seconds.

Dawson & Stenerson Standards Track [Page 37] RFC 2445 iCalendar November 1998

 No additional content value encoding (i.e., BACKSLASH character
 encoding) are defined for this value type.
 Example: A duration of 15 days, 5 hours and 20 seconds would be:
   P15DT5H0M20S
 A duration of 7 weeks would be:
   P7W

4.3.7 Float

 Value Name: FLOAT
 Purpose: This value type is used to identify properties that contain
 a real number value.
 Formal Definition: The value type is defined by the following
 notation:
   float      = (["+"] / "-") 1*DIGIT ["." 1*DIGIT]
 Description: If the property permits, multiple "float" values are
 specified by a COMMA character (US-ASCII decimal 44) separated list
 of values.
 No additional content value encoding (i.e., BACKSLASH character
 encoding) is defined for this value type.
 Example:
   1000000.0000001
   1.333
   -3.14

4.3.8 Integer

   Value Name:INTEGER
   Purpose: This value type is used to identify properties that contain
   a signed integer value.
   Formal Definition: The value type is defined by the following
   notation:
   integer    = (["+"] / "-") 1*DIGIT

Dawson & Stenerson Standards Track [Page 38] RFC 2445 iCalendar November 1998

   Description: If the property permits, multiple "integer" values are
   specified by a COMMA character (US-ASCII decimal 44) separated list
   of values. The valid range for "integer" is -2147483648 to
   2147483647. If the sign is not specified, then the value is assumed
   to be positive.
   No additional content value encoding (i.e., BACKSLASH character
   encoding) is defined for this value type.
   Example:
   1234567890
   -1234567890
   +1234567890
   432109876

4.3.9 Period of Time

 Value Name: PERIOD
 Purpose: This value type is used to identify values that contain a
 precise period of time.
 Formal Definition: The data type is defined by the following
 notation:
   period     = period-explicit / period-start
   period-explicit = date-time "/" date-time
   ; [ISO 8601] complete representation basic format for a period of
   ; time consisting of a start and end. The start MUST be before the
   ; end.
   period-start = date-time "/" dur-value
   ; [ISO 8601] complete representation basic format for a period of
   ; time consisting of a start and positive duration of time.
 Description: If the property permits, multiple "period" values are
 specified by a COMMA character (US-ASCII decimal 44) separated list
 of values. There are two forms of a period of time. First, a period
 of time is identified by its start and its end. This format is
 expressed as the [ISO 8601] complete representation, basic format for
 "DATE-TIME" start of the period, followed by a SOLIDUS character
 (US-ASCII decimal 47), followed by the "DATE-TIME" of the end of the
 period. The start of the period MUST be before the end of the period.
 Second, a period of time can also be defined by a start and a
 positive duration of time. The format is expressed as the [ISO 8601]
 complete representation, basic format for the "DATE-TIME" start of

Dawson & Stenerson Standards Track [Page 39] RFC 2445 iCalendar November 1998

 the period, followed by a SOLIDUS character (US-ASCII decimal 47),
 followed by the [ISO 8601] basic format for "DURATION" of the period.
 Example: The period starting at 18:00:00 UTC, on January 1, 1997 and
 ending at 07:00:00 UTC on January 2, 1997 would be:
   19970101T180000Z/19970102T070000Z
 The period start at 18:00:00 on January 1, 1997 and lasting 5 hours
 and 30 minutes would be:
   19970101T180000Z/PT5H30M
 No additional content value encoding (i.e., BACKSLASH character
 encoding) is defined for this value type.

4.3.10 Recurrence Rule

 Value Name: RECUR
 Purpose: This value type is used to identify properties that contain
 a recurrence rule specification.
 Formal Definition: The value type is defined by the following
 notation:
   recur      = "FREQ"=freq *(
              ; either UNTIL or COUNT may appear in a 'recur',
              ; but UNTIL and COUNT MUST NOT occur in the same 'recur'
              ( ";" "UNTIL" "=" enddate ) /
              ( ";" "COUNT" "=" 1*DIGIT ) /
              ; the rest of these keywords are optional,
              ; but MUST NOT occur more than once
              ( ";" "INTERVAL" "=" 1*DIGIT )          /
              ( ";" "BYSECOND" "=" byseclist )        /
              ( ";" "BYMINUTE" "=" byminlist )        /
              ( ";" "BYHOUR" "=" byhrlist )           /
              ( ";" "BYDAY" "=" bywdaylist )          /
              ( ";" "BYMONTHDAY" "=" bymodaylist )    /
              ( ";" "BYYEARDAY" "=" byyrdaylist )     /
              ( ";" "BYWEEKNO" "=" bywknolist )       /
              ( ";" "BYMONTH" "=" bymolist )          /
              ( ";" "BYSETPOS" "=" bysplist )         /
              ( ";" "WKST" "=" weekday )              /

Dawson & Stenerson Standards Track [Page 40] RFC 2445 iCalendar November 1998

              ( ";" x-name "=" text )
              )
   freq       = "SECONDLY" / "MINUTELY" / "HOURLY" / "DAILY"
              / "WEEKLY" / "MONTHLY" / "YEARLY"
   enddate    = date
   enddate    =/ date-time            ;An UTC value
   byseclist  = seconds / ( seconds *("," seconds) )
   seconds    = 1DIGIT / 2DIGIT       ;0 to 59
   byminlist  = minutes / ( minutes *("," minutes) )
   minutes    = 1DIGIT / 2DIGIT       ;0 to 59
   byhrlist   = hour / ( hour *("," hour) )
   hour       = 1DIGIT / 2DIGIT       ;0 to 23
   bywdaylist = weekdaynum / ( weekdaynum *("," weekdaynum) )
   weekdaynum = [([plus] ordwk / minus ordwk)] weekday
   plus       = "+"
   minus      = "-"
   ordwk      = 1DIGIT / 2DIGIT       ;1 to 53
   weekday    = "SU" / "MO" / "TU" / "WE" / "TH" / "FR" / "SA"
   ;Corresponding to SUNDAY, MONDAY, TUESDAY, WEDNESDAY, THURSDAY,
   ;FRIDAY, SATURDAY and SUNDAY days of the week.
   bymodaylist = monthdaynum / ( monthdaynum *("," monthdaynum) )
   monthdaynum = ([plus] ordmoday) / (minus ordmoday)
   ordmoday   = 1DIGIT / 2DIGIT       ;1 to 31
   byyrdaylist = yeardaynum / ( yeardaynum *("," yeardaynum) )
   yeardaynum = ([plus] ordyrday) / (minus ordyrday)
   ordyrday   = 1DIGIT / 2DIGIT / 3DIGIT      ;1 to 366
   bywknolist = weeknum / ( weeknum *("," weeknum) )

Dawson & Stenerson Standards Track [Page 41] RFC 2445 iCalendar November 1998

   weeknum    = ([plus] ordwk) / (minus ordwk)
   bymolist   = monthnum / ( monthnum *("," monthnum) )
   monthnum   = 1DIGIT / 2DIGIT       ;1 to 12
   bysplist   = setposday / ( setposday *("," setposday) )
   setposday  = yeardaynum
 Description: If the property permits, multiple "recur" values are
 specified by a COMMA character (US-ASCII decimal 44) separated list
 of values. The value type is a structured value consisting of a list
 of one or more recurrence grammar parts. Each rule part is defined by
 a NAME=VALUE pair. The rule parts are separated from each other by
 the SEMICOLON character (US-ASCII decimal 59). The rule parts are not
 ordered in any particular sequence. Individual rule parts MUST only
 be specified once.
 The FREQ rule part identifies the type of recurrence rule. This rule
 part MUST be specified in the recurrence rule. Valid values include
 SECONDLY, to specify repeating events based on an interval of a
 second or more; MINUTELY, to specify repeating events based on an
 interval of a minute or more; HOURLY, to specify repeating events
 based on an interval of an hour or more; DAILY, to specify repeating
 events based on an interval of a day or more; WEEKLY, to specify
 repeating events based on an interval of a week or more; MONTHLY, to
 specify repeating events based on an interval of a month or more; and
 YEARLY, to specify repeating events based on an interval of a year or
 more.
 The INTERVAL rule part contains a positive integer representing how
 often the recurrence rule repeats. The default value is "1", meaning
 every second for a SECONDLY rule, or every minute for a MINUTELY
 rule, every hour for an HOURLY rule, every day for a DAILY rule,
 every week for a WEEKLY rule, every month for a MONTHLY rule and
 every year for a YEARLY rule.
 The UNTIL rule part defines a date-time value which bounds the
 recurrence rule in an inclusive manner. If the value specified by
 UNTIL is synchronized with the specified recurrence, this date or
 date-time becomes the last instance of the recurrence. If specified
 as a date-time value, then it MUST be specified in an UTC time
 format. If not present, and the COUNT rule part is also not present,
 the RRULE is considered to repeat forever.
 The COUNT rule part defines the number of occurrences at which to
 range-bound the recurrence. The "DTSTART" property value, if

Dawson & Stenerson Standards Track [Page 42] RFC 2445 iCalendar November 1998

 specified, counts as the first occurrence.
 The BYSECOND rule part specifies a COMMA character (US-ASCII decimal
 44) separated list of seconds within a minute. Valid values are 0 to
 59. The BYMINUTE rule part specifies a COMMA character (US-ASCII
 decimal 44) separated list of minutes within an hour. Valid values
 are 0 to 59. The BYHOUR rule part specifies a COMMA character (US-
 ASCII decimal 44) separated list of hours of the day. Valid values
 are 0 to 23.
 The BYDAY rule part specifies a COMMA character (US-ASCII decimal 44)
 separated list of days of the week; MO indicates Monday; TU indicates
 Tuesday; WE indicates Wednesday; TH indicates Thursday; FR indicates
 Friday; SA indicates Saturday; SU indicates Sunday.
 Each BYDAY value can also be preceded by a positive (+n) or negative
 (-n) integer. If present, this indicates the nth occurrence of the
 specific day within the MONTHLY or YEARLY RRULE. For example, within
 a MONTHLY rule, +1MO (or simply 1MO) represents the first Monday
 within the month, whereas -1MO represents the last Monday of the
 month. If an integer modifier is not present, it means all days of
 this type within the specified frequency. For example, within a
 MONTHLY rule, MO represents all Mondays within the month.
 The BYMONTHDAY rule part specifies a COMMA character (ASCII decimal
 44) separated list of days of the month. Valid values are 1 to 31 or
 -31 to -1. For example, -10 represents the tenth to the last day of
 the month.
 The BYYEARDAY rule part specifies a COMMA character (US-ASCII decimal
 44) separated list of days of the year. Valid values are 1 to 366 or
 -366 to -1. For example, -1 represents the last day of the year
 (December 31st) and -306 represents the 306th to the last day of the
 year (March 1st).
 The BYWEEKNO rule part specifies a COMMA character (US-ASCII decimal
 44) separated list of ordinals specifying weeks of the year. Valid
 values are 1 to 53 or -53 to -1. This corresponds to weeks according
 to week numbering as defined in [ISO 8601]. A week is defined as a
 seven day period, starting on the day of the week defined to be the
 week start (see WKST). Week number one of the calendar year is the
 first week which contains at least four (4) days in that calendar
 year. This rule part is only valid for YEARLY rules. For example, 3
 represents the third week of the year.
      Note: Assuming a Monday week start, week 53 can only occur when
      Thursday is January 1 or if it is a leap year and Wednesday is
      January 1.

Dawson & Stenerson Standards Track [Page 43] RFC 2445 iCalendar November 1998

 The BYMONTH rule part specifies a COMMA character (US-ASCII decimal
 44) separated list of months of the year. Valid values are 1 to 12.
 The WKST rule part specifies the day on which the workweek starts.
 Valid values are MO, TU, WE, TH, FR, SA and SU. This is significant
 when a WEEKLY RRULE has an interval greater than 1, and a BYDAY rule
 part is specified. This is also significant when in a YEARLY RRULE
 when a BYWEEKNO rule part is specified. The default value is MO.
 The BYSETPOS rule part specifies a COMMA character (US-ASCII decimal
 44) separated list of values which corresponds to the nth occurrence
 within the set of events specified by the rule. Valid values are 1 to
 366 or -366 to -1. It MUST only be used in conjunction with another
 BYxxx rule part. For example "the last work day of the month" could
 be represented as:
   RRULE:FREQ=MONTHLY;BYDAY=MO,TU,WE,TH,FR;BYSETPOS=-1
 Each BYSETPOS value can include a positive (+n) or negative (-n)
 integer. If present, this indicates the nth occurrence of the
 specific occurrence within the set of events specified by the rule.
 If BYxxx rule part values are found which are beyond the available
 scope (ie, BYMONTHDAY=30 in February), they are simply ignored.
 Information, not contained in the rule, necessary to determine the
 various recurrence instance start time and dates are derived from the
 Start Time (DTSTART) entry attribute. For example,
 "FREQ=YEARLY;BYMONTH=1" doesn't specify a specific day within the
 month or a time. This information would be the same as what is
 specified for DTSTART.
 BYxxx rule parts modify the recurrence in some manner. BYxxx rule
 parts for a period of time which is the same or greater than the
 frequency generally reduce or limit the number of occurrences of the
 recurrence generated. For example, "FREQ=DAILY;BYMONTH=1" reduces the
 number of recurrence instances from all days (if BYMONTH tag is not
 present) to all days in January. BYxxx rule parts for a period of
 time less than the frequency generally increase or expand the number
 of occurrences of the recurrence. For example,
 "FREQ=YEARLY;BYMONTH=1,2" increases the number of days within the
 yearly recurrence set from 1 (if BYMONTH tag is not present) to 2.
 If multiple BYxxx rule parts are specified, then after evaluating the
 specified FREQ and INTERVAL rule parts, the BYxxx rule parts are
 applied to the current set of evaluated occurrences in the following
 order: BYMONTH, BYWEEKNO, BYYEARDAY, BYMONTHDAY, BYDAY, BYHOUR,
 BYMINUTE, BYSECOND and BYSETPOS; then COUNT and UNTIL are evaluated.

Dawson & Stenerson Standards Track [Page 44] RFC 2445 iCalendar November 1998

 Here is an example of evaluating multiple BYxxx rule parts.
   DTSTART;TZID=US-Eastern:19970105T083000
   RRULE:FREQ=YEARLY;INTERVAL=2;BYMONTH=1;BYDAY=SU;BYHOUR=8,9;
    BYMINUTE=30
 First, the "INTERVAL=2" would be applied to "FREQ=YEARLY" to arrive
 at "every other year". Then, "BYMONTH=1" would be applied to arrive
 at "every January, every other year". Then, "BYDAY=SU" would be
 applied to arrive at "every Sunday in January, every other year".
 Then, "BYHOUR=8,9" would be applied to arrive at "every Sunday in
 January at 8 AM and 9 AM, every other year". Then, "BYMINUTE=30"
 would be applied to arrive at "every Sunday in January at 8:30 AM and
 9:30 AM, every other year". Then, lacking information from RRULE, the
 second is derived from DTSTART, to end up in "every Sunday in January
 at 8:30:00 AM and 9:30:00 AM, every other year". Similarly, if the
 BYMINUTE, BYHOUR, BYDAY, BYMONTHDAY or BYMONTH rule part were
 missing, the appropriate minute, hour, day or month would have been
 retrieved from the "DTSTART" property.
 No additional content value encoding (i.e., BACKSLASH character
 encoding) is defined for this value type.
 Example: The following is a rule which specifies 10 meetings which
 occur every other day:
   FREQ=DAILY;COUNT=10;INTERVAL=2
 There are other examples specified in the "RRULE" specification.

4.3.11 Text

 Value Name: TEXT
 Purpose This value type is used to identify values that contain human
 readable text.
 Formal Definition: The character sets supported by this revision of
 iCalendar are UTF-8 and US ASCII thereof. The applicability to other
 character sets is for future work. The value type is defined by the
 following notation.
   text       = *(TSAFE-CHAR / ":" / DQUOTE / ESCAPED-CHAR)
   ; Folded according to description above
   ESCAPED-CHAR = "\\" / "\;" / "\," / "\N" / "\n")
      ; \\ encodes \, \N or \n encodes newline
      ; \; encodes ;, \, encodes ,

Dawson & Stenerson Standards Track [Page 45] RFC 2445 iCalendar November 1998

   TSAFE-CHAR = %x20-21 / %x23-2B / %x2D-39 / %x3C-5B
                %x5D-7E / NON-US-ASCII
      ; Any character except CTLs not needed by the current
      ; character set, DQUOTE, ";", ":", "\", ","
   Note: Certain other character sets may require modification of the
   above definitions, but this is beyond the scope of this document.
 Description: If the property permits, multiple "text" values are
 specified by a COMMA character (US-ASCII decimal 44) separated list
 of values.
 The language in which the text is represented can be controlled by
 the "LANGUAGE" property parameter.
 An intentional formatted text line break MUST only be included in a
 "TEXT" property value by representing the line break with the
 character sequence of BACKSLASH (US-ASCII decimal 92), followed by a
 LATIN SMALL LETTER N (US-ASCII decimal 110) or a LATIN CAPITAL LETTER
 N (US-ASCII decimal 78), that is "\n" or "\N".
 The "TEXT" property values may also contain special characters that
 are used to signify delimiters, such as a COMMA character for lists
 of values or a SEMICOLON character for structured values. In order to
 support the inclusion of these special characters in "TEXT" property
 values, they MUST be escaped with a BACKSLASH character. A BACKSLASH
 character (US-ASCII decimal 92) in a "TEXT" property value MUST be
 escaped with another BACKSLASH character. A COMMA character in a
 "TEXT" property value MUST be escaped with a BACKSLASH character
 (US-ASCII decimal 92). A SEMICOLON character in a "TEXT" property
 value MUST be escaped with a BACKSLASH character (US-ASCII decimal
 92).  However, a COLON character in a "TEXT" property value SHALL NOT
 be escaped with a BACKSLASH character.Example: A multiple line value
 of:
   Project XYZ Final Review
   Conference Room - 3B
   Come Prepared.
 would be represented as:
   Project XYZ Final Review\nConference Room - 3B\nCome Prepared.

Dawson & Stenerson Standards Track [Page 46] RFC 2445 iCalendar November 1998

4.3.12 Time

 Value Name: TIME
 Purpose: This value type is used to identify values that contain a
 time of day.
 Formal Definition: The data type is defined by the following
 notation:
   time               = time-hour time-minute time-second [time-utc]
   time-hour          = 2DIGIT        ;00-23
   time-minute        = 2DIGIT        ;00-59
   time-second        = 2DIGIT        ;00-60
   ;The "60" value is used to account for "leap" seconds.
   time-utc   = "Z"
 Description: If the property permits, multiple "time" values are
 specified by a COMMA character (US-ASCII decimal 44) separated list
 of values. No additional content value encoding (i.e., BACKSLASH
 character encoding) is defined for this value type.
 The "TIME" data type is used to identify values that contain a time
 of day. The format is based on the [ISO 8601] complete
 representation, basic format for a time of day. The text format
 consists of a two-digit 24-hour of the day (i.e., values 0-23), two-
 digit minute in the hour (i.e., values 0-59), and two-digit seconds
 in the minute (i.e., values 0-60). The seconds value of 60 MUST only
 to be used to account for "leap" seconds. Fractions of a second are
 not supported by this format.
 In parallel to the "DATE-TIME" definition above, the "TIME" data type
 expresses time values in three forms:
 The form of time with UTC offset MUST NOT be used. For example, the
 following is NOT VALID for a time value:
   230000-0800        ;Invalid time format
 FORM #1 LOCAL TIME
 The local time form is simply a time value that does not contain the
 UTC designator nor does it reference a time zone. For example, 11:00
 PM:
   230000

Dawson & Stenerson Standards Track [Page 47] RFC 2445 iCalendar November 1998

 Time values of this type are said to be "floating" and are not bound
 to any time zone in particular. They are used to represent the same
 hour, minute, and second value regardless of which time zone is
 currently being observed. For example, an event can be defined that
 indicates that an individual will be busy from 11:00 AM to 1:00 PM
 every day, no matter which time zone the person is in. In these
 cases, a local time can be specified. The recipient of an iCalendar
 object with a property value consisting of a local time, without any
 relative time zone information, SHOULD interpret the value as being
 fixed to whatever time zone the ATTENDEE is in at any given moment.
 This means that two ATTENDEEs may participate in the same event at
 different UTC times; floating time SHOULD only be used where that is
 reasonable behavior.
 In most cases, a fixed time is desired. To properly communicate a
 fixed time in a property value, either UTC time or local time with
 time zone reference MUST be specified.
 The use of local time in a TIME value without the TZID property
 parameter is to be interpreted as a local time value, regardless of
 the existence of "VTIMEZONE" calendar components in the iCalendar
 object.
 FORM #2: UTC TIME
 UTC time, or absolute time, is identified by a LATIN CAPITAL LETTER Z
 suffix character (US-ASCII decimal 90), the UTC designator, appended
 to the time value. For example, the following represents 07:00 AM
 UTC:
   070000Z
 The TZID property parameter MUST NOT be applied to TIME properties
 whose time values are specified in UTC.
 FORM #3: LOCAL TIME AND TIME ZONE REFERENCE
 The local time with reference to time zone information form is
 identified by the use the TZID property parameter to reference the
 appropriate time zone definition. TZID is discussed in detail in the
 section on Time Zone.
 Example: The following represents 8:30 AM in New York in Winter, five
 hours behind UTC, in each of the three formats using the "X-
 TIMEOFDAY" non-standard property:

Dawson & Stenerson Standards Track [Page 48] RFC 2445 iCalendar November 1998

   X-TIMEOFDAY:083000
   X-TIMEOFDAY:133000Z
   X-TIMEOFDAY;TZID=US-Eastern:083000

4.3.13 URI

 Value Name: URI
 Purpose: This value type is used to identify values that contain a
 uniform resource identifier (URI) type of reference to the property
 value.
 Formal Definition: The data type is defined by the following
 notation:
   uri        = <As defined by any IETF RFC>
 Description: This data type might be used to reference binary
 information, for values that are large, or otherwise undesirable to
 include directly in the iCalendar object.
 The URI value formats in RFC 1738, RFC 2111 and any other IETF
 registered value format can be specified.
 Any IANA registered URI format can be used. These include, but are
 not limited to, those defined in RFC 1738 and RFC 2111.
 When a property parameter value is a URI value type, the URI MUST be
 specified as a quoted-string value.
 No additional content value encoding (i.e., BACKSLASH character
 encoding) is defined for this value type.
 Example: The following is a URI for a network file:
   http://host1.com/my-report.txt

4.3.14 UTC Offset

 Value Name: UTC-OFFSET
 Purpose: This value type is used to identify properties that contain
 an offset from UTC to local time.
 Formal Definition: The data type is defined by the following
 notation:

Dawson & Stenerson Standards Track [Page 49] RFC 2445 iCalendar November 1998

   utc-offset = time-numzone  ;As defined above in time data type
   time-numzone       = ("+" / "-") time-hour time-minute [time-
   second]
 Description: The PLUS SIGN character MUST be specified for positive
 UTC offsets (i.e., ahead of UTC). The value of "-0000" and "-000000"
 are not allowed. The time-second, if present, may not be 60; if
 absent, it defaults to zero.
 No additional content value encoding (i.e., BACKSLASH character
 encoding) is defined for this value type.
 Example: The following UTC offsets are given for standard time for
 New York (five hours behind UTC) and Geneva (one hour ahead of UTC):
  1. 0500
   +0100

4.4 iCalendar Object

 The Calendaring and Scheduling Core Object is a collection of
 calendaring and scheduling information. Typically, this information
 will consist of a single iCalendar object. However, multiple
 iCalendar objects can be sequentially grouped together. The first
 line and last line of the iCalendar object MUST contain a pair of
 iCalendar object delimiter strings. The syntax for an iCalendar
 object is as follows:
   icalobject = 1*("BEGIN" ":" "VCALENDAR" CRLF
                icalbody
                "END" ":" "VCALENDAR" CRLF)
 The following is a simple example of an iCalendar object:
   BEGIN:VCALENDAR
   VERSION:2.0
   PRODID:-//hacksw/handcal//NONSGML v1.0//EN
   BEGIN:VEVENT
   DTSTART:19970714T170000Z
   DTEND:19970715T035959Z
   SUMMARY:Bastille Day Party
   END:VEVENT
   END:VCALENDAR

Dawson & Stenerson Standards Track [Page 50] RFC 2445 iCalendar November 1998

4.5 Property

 A property is the definition of an individual attribute describing a
 calendar or a calendar component. A property takes the form defined
 by the "contentline" notation defined in section 4.1.1.
 The following is an example of a property:
   DTSTART:19960415T133000Z
 This memo imposes no ordering of properties within an iCalendar
 object.
 Property names, parameter names and enumerated parameter values are
 case insensitive. For example, the property name "DUE" is the same as
 "due" and "Due", DTSTART;TZID=US-Eastern:19980714T120000 is the same
 as DtStart;TzID=US-Eastern:19980714T120000.

4.6 Calendar Components

 The body of the iCalendar object consists of a sequence of calendar
 properties and one or more calendar components. The calendar
 properties are attributes that apply to the calendar as a whole. The
 calendar components are collections of properties that express a
 particular calendar semantic. For example, the calendar component can
 specify an event, a to-do, a journal entry, time zone information, or
 free/busy time information, or an alarm.
 The body of the iCalendar object is defined by the following
 notation:
   icalbody   = calprops component
   calprops   = 2*(
              ; 'prodid' and 'version' are both REQUIRED,
              ; but MUST NOT occur more than once
              prodid /version /
              ; 'calscale' and 'method' are optional,
              ; but MUST NOT occur more than once
              calscale        /
              method          /
              x-prop

Dawson & Stenerson Standards Track [Page 51] RFC 2445 iCalendar November 1998

              )
   component  = 1*(eventc / todoc / journalc / freebusyc /
              / timezonec / iana-comp / x-comp)
   iana-comp  = "BEGIN" ":" iana-token CRLF
                1*contentline
                "END" ":" iana-token CRLF
   x-comp     = "BEGIN" ":" x-name CRLF
                1*contentline
                "END" ":" x-name CRLF
 An iCalendar object MUST include the "PRODID" and "VERSION" calendar
 properties. In addition, it MUST include at least one calendar
 component. Special forms of iCalendar objects are possible to publish
 just busy time (i.e., only a "VFREEBUSY" calendar component) or time
 zone (i.e., only a "VTIMEZONE" calendar component) information. In
 addition, a complex iCalendar object is possible that is used to
 capture a complete snapshot of the contents of a calendar (e.g.,
 composite of many different calendar components). More commonly, an
 iCalendar object will consist of just a single "VEVENT", "VTODO" or
 "VJOURNAL" calendar component.

4.6.1 Event Component

 Component Name: "VEVENT"
 Purpose: Provide a grouping of component properties that describe an
 event.
 Format Definition: A "VEVENT" calendar component is defined by the
 following notation:
   eventc     = "BEGIN" ":" "VEVENT" CRLF
                eventprop *alarmc
                "END" ":" "VEVENT" CRLF
   eventprop  = *(
              ; the following are optional,
              ; but MUST NOT occur more than once
              class / created / description / dtstart / geo /

Dawson & Stenerson Standards Track [Page 52] RFC 2445 iCalendar November 1998

              last-mod / location / organizer / priority /
              dtstamp / seq / status / summary / transp /
              uid / url / recurid /
              ; either 'dtend' or 'duration' may appear in
              ; a 'eventprop', but 'dtend' and 'duration'
              ; MUST NOT occur in the same 'eventprop'
              dtend / duration /
              ; the following are optional,
              ; and MAY occur more than once
              attach / attendee / categories / comment /
              contact / exdate / exrule / rstatus / related /
              resources / rdate / rrule / x-prop
              )
 Description: A "VEVENT" calendar component is a grouping of component
 properties, and possibly including "VALARM" calendar components, that
 represents a scheduled amount of time on a calendar. For example, it
 can be an activity; such as a one-hour long, department meeting from
 8:00 AM to 9:00 AM, tomorrow. Generally, an event will take up time
 on an individual calendar. Hence, the event will appear as an opaque
 interval in a search for busy time. Alternately, the event can have
 its Time Transparency set to "TRANSPARENT" in order to prevent
 blocking of the event in searches for busy time.
 The "VEVENT" is also the calendar component used to specify an
 anniversary or daily reminder within a calendar. These events have a
 DATE value type for the "DTSTART" property instead of the default
 data type of DATE-TIME. If such a "VEVENT" has a "DTEND" property, it
 MUST be specified as a DATE value also. The anniversary type of
 "VEVENT" can span more than one date (i.e, "DTEND" property value is
 set to a calendar date after the "DTSTART" property value).
 The "DTSTART" property for a "VEVENT" specifies the inclusive start
 of the event. For recurring events, it also specifies the very first
 instance in the recurrence set. The "DTEND" property for a "VEVENT"
 calendar component specifies the non-inclusive end of the event. For
 cases where a "VEVENT" calendar component specifies a "DTSTART"
 property with a DATE data type but no "DTEND" property, the events
 non-inclusive end is the end of the calendar date specified by the
 "DTSTART" property. For cases where a "VEVENT" calendar component
 specifies a "DTSTART" property with a DATE-TIME data type but no
 "DTEND" property, the event ends on the same calendar date and time
 of day specified by the "DTSTART" property.

Dawson & Stenerson Standards Track [Page 53] RFC 2445 iCalendar November 1998

 The "VEVENT" calendar component cannot be nested within another
 calendar component. However, "VEVENT" calendar components can be
 related to each other or to a "VTODO" or to a "VJOURNAL" calendar
 component with the "RELATED-TO" property.
 Example: The following is an example of the "VEVENT" calendar
 component used to represent a meeting that will also be opaque to
 searches for busy time:
   BEGIN:VEVENT
   UID:19970901T130000Z-123401@host.com
   DTSTAMP:19970901T1300Z
   DTSTART:19970903T163000Z
   DTEND:19970903T190000Z
   SUMMARY:Annual Employee Review
   CLASS:PRIVATE
   CATEGORIES:BUSINESS,HUMAN RESOURCES
   END:VEVENT
 The following is an example of the "VEVENT" calendar component used
 to represent a reminder that will not be opaque, but rather
 transparent, to searches for busy time:
   BEGIN:VEVENT
   UID:19970901T130000Z-123402@host.com
   DTSTAMP:19970901T1300Z
   DTSTART:19970401T163000Z
   DTEND:19970402T010000Z
   SUMMARY:Laurel is in sensitivity awareness class.
   CLASS:PUBLIC
   CATEGORIES:BUSINESS,HUMAN RESOURCES
   TRANSP:TRANSPARENT
   END:VEVENT
 The following is an example of the "VEVENT" calendar component used
 to represent an anniversary that will occur annually. Since it takes
 up no time, it will not appear as opaque in a search for busy time;
 no matter what the value of the "TRANSP" property indicates:
   BEGIN:VEVENT
   UID:19970901T130000Z-123403@host.com
   DTSTAMP:19970901T1300Z
   DTSTART:19971102
   SUMMARY:Our Blissful Anniversary
   CLASS:CONFIDENTIAL
   CATEGORIES:ANNIVERSARY,PERSONAL,SPECIAL OCCASION
   RRULE:FREQ=YEARLY
   END:VEVENT

Dawson & Stenerson Standards Track [Page 54] RFC 2445 iCalendar November 1998

4.6.2 To-do Component

 Component Name: VTODO
 Purpose: Provide a grouping of calendar properties that describe a
 to-do.
 Formal Definition: A "VTODO" calendar component is defined by the
 following notation:
   todoc      = "BEGIN" ":" "VTODO" CRLF
                todoprop *alarmc
                "END" ":" "VTODO" CRLF
   todoprop   = *(
              ; the following are optional,
              ; but MUST NOT occur more than once
              class / completed / created / description / dtstamp /
              dtstart / geo / last-mod / location / organizer /
              percent / priority / recurid / seq / status /
              summary / uid / url /
              ; either 'due' or 'duration' may appear in
              ; a 'todoprop', but 'due' and 'duration'
              ; MUST NOT occur in the same 'todoprop'
              due / duration /
              ; the following are optional,
              ; and MAY occur more than once
              attach / attendee / categories / comment / contact /
              exdate / exrule / rstatus / related / resources /
              rdate / rrule / x-prop
              )
 Description: A "VTODO" calendar component is a grouping of component
 properties and possibly "VALARM" calendar components that represent
 an action-item or assignment. For example, it can be used to
 represent an item of work assigned to an individual; such as "turn in
 travel expense today".
 The "VTODO" calendar component cannot be nested within another
 calendar component. However, "VTODO" calendar components can be
 related to each other or to a "VTODO" or to a "VJOURNAL" calendar
 component with the "RELATED-TO" property.

Dawson & Stenerson Standards Track [Page 55] RFC 2445 iCalendar November 1998

 A "VTODO" calendar component without the "DTSTART" and "DUE" (or
 "DURATION") properties specifies a to-do that will be associated with
 each successive calendar date, until it is completed.
 Example: The following is an example of a "VTODO" calendar component:
   BEGIN:VTODO
   UID:19970901T130000Z-123404@host.com
   DTSTAMP:19970901T1300Z
   DTSTART:19970415T133000Z
   DUE:19970416T045959Z
   SUMMARY:1996 Income Tax Preparation
   CLASS:CONFIDENTIAL
   CATEGORIES:FAMILY,FINANCE
   PRIORITY:1
   STATUS:NEEDS-ACTION
   END:VTODO

4.6.3 Journal Component

 Component Name: VJOURNAL
 Purpose: Provide a grouping of component properties that describe a
 journal entry.
 Formal Definition: A "VJOURNAL" calendar component is defined by the
 following notation:
   journalc   = "BEGIN" ":" "VJOURNAL" CRLF
                jourprop
                "END" ":" "VJOURNAL" CRLF
   jourprop   = *(
              ; the following are optional,
              ; but MUST NOT occur more than once
              class / created / description / dtstart / dtstamp /
              last-mod / organizer / recurid / seq / status /
              summary / uid / url /
              ; the following are optional,
              ; and MAY occur more than once
              attach / attendee / categories / comment /
              contact / exdate / exrule / related / rdate /
              rrule / rstatus / x-prop

Dawson & Stenerson Standards Track [Page 56] RFC 2445 iCalendar November 1998

              )
 Description: A "VJOURNAL" calendar component is a grouping of
 component properties that represent one or more descriptive text
 notes associated with a particular calendar date. The "DTSTART"
 property is used to specify the calendar date that the journal entry
 is associated with. Generally, it will have a DATE value data type,
 but it can also be used to specify a DATE-TIME value data type.
 Examples of a journal entry include a daily record of a legislative
 body or a journal entry of individual telephone contacts for the day
 or an ordered list of accomplishments for the day. The "VJOURNAL"
 calendar component can also be used to associate a document with a
 calendar date.
 The "VJOURNAL" calendar component does not take up time on a
 calendar. Hence, it does not play a role in free or busy time
 searches - - it is as though it has a time transparency value of
 TRANSPARENT. It is transparent to any such searches.
 The "VJOURNAL" calendar component cannot be nested within another
 calendar component. However, "VJOURNAL" calendar components can be
 related to each other or to a "VEVENT" or to a "VTODO" calendar
 component, with the "RELATED-TO" property.
 Example: The following is an example of the "VJOURNAL" calendar
 component:
   BEGIN:VJOURNAL
   UID:19970901T130000Z-123405@host.com
   DTSTAMP:19970901T1300Z
   DTSTART;VALUE=DATE:19970317
   SUMMARY:Staff meeting minutes
   DESCRIPTION:1. Staff meeting: Participants include Joe\, Lisa
     and Bob. Aurora project plans were reviewed. There is currently
     no budget reserves for this project. Lisa will escalate to
     management. Next meeting on Tuesday.\n
     2. Telephone Conference: ABC Corp. sales representative called
     to discuss new printer. Promised to get us a demo by Friday.\n
     3. Henry Miller (Handsoff Insurance): Car was totaled by tree.
     Is looking into a loaner car. 654-2323 (tel).
   END:VJOURNAL

Dawson & Stenerson Standards Track [Page 57] RFC 2445 iCalendar November 1998

4.6.4 Free/Busy Component

 Component Name: VFREEBUSY
 Purpose: Provide a grouping of component properties that describe
 either a request for free/busy time, describe a response to a request
 for free/busy time or describe a published set of busy time.
 Formal Definition: A "VFREEBUSY" calendar component is defined by the
 following notation:
   freebusyc  = "BEGIN" ":" "VFREEBUSY" CRLF
                fbprop
                "END" ":" "VFREEBUSY" CRLF
   fbprop     = *(
              ; the following are optional,
              ; but MUST NOT occur more than once
              contact / dtstart / dtend / duration / dtstamp /
              organizer / uid / url /
              ; the following are optional,
              ; and MAY occur more than once
              attendee / comment / freebusy / rstatus / x-prop
              )
 Description: A "VFREEBUSY" calendar component is a grouping of
 component properties that represents either a request for, a reply to
 a request for free or busy time information or a published set of
 busy time information.
 When used to request free/busy time information, the "ATTENDEE"
 property specifies the calendar users whose free/busy time is being
 requested; the "ORGANIZER" property specifies the calendar user who
 is requesting the free/busy time; the "DTSTART" and "DTEND"
 properties specify the window of time for which the free/busy time is
 being requested; the "UID" and "DTSTAMP" properties are specified to
 assist in proper sequencing of multiple free/busy time requests.
 When used to reply to a request for free/busy time, the "ATTENDEE"
 property specifies the calendar user responding to the free/busy time
 request; the "ORGANIZER" property specifies the calendar user that
 originally requested the free/busy time; the "FREEBUSY" property
 specifies the free/busy time information (if it exists); and the

Dawson & Stenerson Standards Track [Page 58] RFC 2445 iCalendar November 1998

 "UID" and "DTSTAMP" properties are specified to assist in proper
 sequencing of multiple free/busy time replies.
 When used to publish busy time, the "ORGANIZER" property specifies
 the calendar user associated with the published busy time; the
 "DTSTART" and "DTEND" properties specify an inclusive time window
 that surrounds the busy time information; the "FREEBUSY" property
 specifies the published busy time information; and the "DTSTAMP"
 property specifies the date/time that iCalendar object was created.
 The "VFREEBUSY" calendar component cannot be nested within another
 calendar component. Multiple "VFREEBUSY" calendar components can be
 specified within an iCalendar object. This permits the grouping of
 Free/Busy information into logical collections, such as monthly
 groups of busy time information.
 The "VFREEBUSY" calendar component is intended for use in iCalendar
 object methods involving requests for free time, requests for busy
 time, requests for both free and busy, and the associated replies.
 Free/Busy information is represented with the "FREEBUSY" property.
 This property provides a terse representation of time periods. One or
 more "FREEBUSY" properties can be specified in the "VFREEBUSY"
 calendar component.
 When present in a "VFREEBUSY" calendar component, the "DTSTART" and
 "DTEND" properties SHOULD be specified prior to any "FREEBUSY"
 properties. In a free time request, these properties can be used in
 combination with the "DURATION" property to represent a request for a
 duration of free time within a specified window of time.
 The recurrence properties ("RRULE", "EXRULE", "RDATE", "EXDATE") are
 not permitted within a "VFREEBUSY" calendar component. Any recurring
 events are resolved into their individual busy time periods using the
 "FREEBUSY" property.
 Example: The following is an example of a "VFREEBUSY" calendar
 component used to request free or busy time information:
   BEGIN:VFREEBUSY
   ORGANIZER:MAILTO:jane_doe@host1.com
   ATTENDEE:MAILTO:john_public@host2.com
   DTSTART:19971015T050000Z
   DTEND:19971016T050000Z
   DTSTAMP:19970901T083000Z
   END:VFREEBUSY

Dawson & Stenerson Standards Track [Page 59] RFC 2445 iCalendar November 1998

 The following is an example of a "VFREEBUSY" calendar component used
 to reply to the request with busy time information:
   BEGIN:VFREEBUSY
   ORGANIZER:MAILTO:jane_doe@host1.com
   ATTENDEE:MAILTO:john_public@host2.com
   DTSTAMP:19970901T100000Z
   FREEBUSY;VALUE=PERIOD:19971015T050000Z/PT8H30M,
    19971015T160000Z/PT5H30M,19971015T223000Z/PT6H30M
   URL:http://host2.com/pub/busy/jpublic-01.ifb
   COMMENT:This iCalendar file contains busy time information for
     the next three months.
   END:VFREEBUSY
 The following is an example of a "VFREEBUSY" calendar component used
 to publish busy time information.
   BEGIN:VFREEBUSY
   ORGANIZER:jsmith@host.com
   DTSTART:19980313T141711Z
   DTEND:19980410T141711Z
   FREEBUSY:19980314T233000Z/19980315T003000Z
   FREEBUSY:19980316T153000Z/19980316T163000Z
   FREEBUSY:19980318T030000Z/19980318T040000Z
   URL:http://www.host.com/calendar/busytime/jsmith.ifb
   END:VFREEBUSY

4.6.5 Time Zone Component

 Component Name: VTIMEZONE
 Purpose: Provide a grouping of component properties that defines a
 time zone.
 Formal Definition: A "VTIMEZONE" calendar component is defined by the
 following notation:
   timezonec  = "BEGIN" ":" "VTIMEZONE" CRLF
                2*(
                ; 'tzid' is required, but MUST NOT occur more
                ; than once
              tzid /
                ; 'last-mod' and 'tzurl' are optional,
              but MUST NOT occur more than once

Dawson & Stenerson Standards Track [Page 60] RFC 2445 iCalendar November 1998

              last-mod / tzurl /
                ; one of 'standardc' or 'daylightc' MUST occur
              ..; and each MAY occur more than once.
              standardc / daylightc /
              ; the following is optional,
              ; and MAY occur more than once
                x-prop
                )
                "END" ":" "VTIMEZONE" CRLF
   standardc  = "BEGIN" ":" "STANDARD" CRLF
                tzprop
                "END" ":" "STANDARD" CRLF
   daylightc  = "BEGIN" ":" "DAYLIGHT" CRLF
                tzprop
                "END" ":" "DAYLIGHT" CRLF
   tzprop     = 3*(
              ; the following are each REQUIRED,
              ; but MUST NOT occur more than once
              dtstart / tzoffsetto / tzoffsetfrom /
              ; the following are optional,
              ; and MAY occur more than once
              comment / rdate / rrule / tzname / x-prop
              )
 Description: A time zone is unambiguously defined by the set of time
 measurement rules determined by the governing body for a given
 geographic area. These rules describe at a minimum the base  offset
 from UTC for the time zone, often referred to as the Standard Time
 offset. Many locations adjust their Standard Time forward or backward
 by one hour, in order to accommodate seasonal changes in number of

Dawson & Stenerson Standards Track [Page 61] RFC 2445 iCalendar November 1998

 daylight hours, often referred to as Daylight  Saving Time. Some
 locations adjust their time by a fraction of an hour. Standard Time
 is also known as Winter Time. Daylight Saving Time is also known as
 Advanced Time, Summer Time, or Legal Time in certain countries. The
 following table shows the changes in time zone rules in effect for
 New York City starting from 1967. Each line represents a description
 or rule for a particular observance.
   Effective Observance Rule
   Date       (Date/Time)             Offset  Abbreviation
   1967-*     last Sun in Oct, 02:00  -0500   EST
   1967-1973  last Sun in Apr, 02:00  -0400   EDT
   1974-1974  Jan 6,  02:00           -0400   EDT
   1975-1975  Feb 23, 02:00           -0400   EDT
   1976-1986  last Sun in Apr, 02:00  -0400   EDT
   1987-*     first Sun in Apr, 02:00 -0400   EDT
      Note: The specification of a global time zone registry is not
      addressed by this document and is left for future study.
      However, implementers may find the Olson time zone database [TZ]
      a useful reference. It is an informal, public-domain collection
      of time zone information, which is currently being maintained by
      volunteer Internet participants, and is used in several
      operating systems. This database contains current and historical
      time zone information for a wide variety of locations around the
      globe; it provides a time zone identifier for every unique time
      zone rule set in actual use since 1970, with historical data
      going back to the introduction of standard time.
 Interoperability between two calendaring and scheduling applications,
 especially for recurring events, to-dos or journal entries, is
 dependent on the ability to capture and convey date and time
 information in an unambiguous format. The specification of current
 time zone information is integral to this behavior.
 If present, the "VTIMEZONE" calendar component defines the set of
 Standard Time and Daylight Saving Time observances (or rules) for a
 particular time zone for a given interval of time. The "VTIMEZONE"
 calendar component cannot be nested within other calendar components.
 Multiple "VTIMEZONE" calendar components can exist in an iCalendar
 object. In this situation, each "VTIMEZONE" MUST represent a unique

Dawson & Stenerson Standards Track [Page 62] RFC 2445 iCalendar November 1998

 time zone definition. This is necessary for some classes of events,
 such as airline flights, that start in one time zone and end in
 another.
 The "VTIMEZONE" calendar component MUST be present if the iCalendar
 object contains an RRULE that generates dates on both sides of a time
 zone shift (e.g. both in Standard Time and Daylight Saving Time)
 unless the iCalendar object intends to convey a floating time (See
 the section "4.1.10.11 Time" for proper interpretation of floating
 time). It can be present if the iCalendar object does not contain
 such a RRULE. In addition, if a RRULE is present, there MUST be valid
 time zone information for all recurrence instances.
 The "VTIMEZONE" calendar component MUST include the "TZID" property
 and at least one definition of a standard or daylight component. The
 standard or daylight component MUST include the "DTSTART",
 "TZOFFSETFROM" and "TZOFFSETTO" properties.
 An individual "VTIMEZONE" calendar component MUST be specified for
 each unique "TZID" parameter value specified in the iCalendar object.
 Each "VTIMEZONE" calendar component consists of a collection of one
 or more sub-components that describe the rule for a particular
 observance (either a Standard Time or a Daylight Saving Time
 observance). The "STANDARD" sub-component consists of a collection of
 properties that describe Standard Time. The "DAYLIGHT" sub-component
 consists of a collection of properties that describe Daylight Saving
 Time. In general this collection of properties consists of:
  1. the first onset date-time for the observance
  1. the last onset date-time for the observance, if a last onset

is known.

  1. the offset to be applied for the observance
  1. a rule that describes the day and time when the observance

takes effect

  1. an optional name for the observance
 For a given time zone, there may be multiple unique definitions of
 the observances over a period of time. Each observance is described
 using either a "STANDARD" or "DAYLIGHT" sub-component. The collection
 of these sub-components is used to describe the time zone for a given
 period of time. The offset to apply at any given time is found by
 locating the observance that has the last onset date and time before
 the time in question, and using the offset value from that

Dawson & Stenerson Standards Track [Page 63] RFC 2445 iCalendar November 1998

 observance.
 The top-level properties in a "VTIMEZONE" calendar component are:
 The mandatory "TZID" property is a text value that uniquely
 identifies the VTIMZONE calendar component within the scope of an
 iCalendar object.
 The optional "LAST-MODIFIED" property is a UTC value that specifies
 the date and time that this time zone definition was last updated.
 The optional "TZURL" property is url value that points to a published
 VTIMEZONE definition. TZURL SHOULD refer to a resource that is
 accessible by anyone who might need to interpret the object. This
 SHOULD NOT normally be a file: URL or other URL that is not widely-
 accessible.
 The collection of properties that are used to define the STANDARD and
 DAYLIGHT sub-components include:
 The mandatory "DTSTART" property gives the effective onset date and
 local time for the time zone sub-component definition. "DTSTART" in
 this usage MUST be specified as a local DATE-TIME value.
 The mandatory "TZOFFSETFROM" property gives the UTC offset which is
 in use when the onset of this time zone observance begins.
 "TZOFFSETFROM" is combined with "DTSTART" to define the effective
 onset for the time zone sub-component definition. For example, the
 following represents the time at which the observance of Standard
 Time took effect in Fall 1967 for New York City:
   DTSTART:19671029T020000
   TZOFFSETFROM:-0400
 The mandatory "TZOFFSETTO " property gives the UTC offset for the
 time zone sub-component (Standard Time or Daylight Saving Time) when
 this observance is in use.
 The optional "TZNAME" property is the customary name for the time
 zone. It may be specified multiple times, to allow for specifying
 multiple language variants of the time zone names. This could be used
 for displaying dates.
 If specified, the onset for the observance defined by the time zone
 sub-component is defined by either the "RRULE" or "RDATE" property.
 If neither is specified, only one sub-component can be specified in
 the "VTIMEZONE" calendar component and it is assumed that the single

Dawson & Stenerson Standards Track [Page 64] RFC 2445 iCalendar November 1998

 observance specified is always in effect.
 The "RRULE" property defines the recurrence rule for the onset of the
 observance defined by this time zone sub-component. Some specific
 requirements for the usage of RRULE for this purpose include:
  1. If observance is known to have an effective end date, the

"UNTIL" recurrence rule parameter MUST be used to specify the

      last valid onset of this observance (i.e., the UNTIL date-time
      will be equal to the last instance generated by the recurrence
      pattern). It MUST be specified in UTC time.
  1. The "DTSTART" and the "TZOFFSETTO" properties MUST be used

when generating the onset date-time values (instances) from the

      RRULE.
 Alternatively, the "RDATE" property can be used to define the onset
 of the observance by giving the individual onset date and times.
 "RDATE" in this usage MUST be specified as a local DATE-TIME value in
 UTC time.
 The optional "COMMENT" property is also allowed for descriptive
 explanatory text.
 Example: The following are examples of the "VTIMEZONE" calendar
 component:
 This is an example showing time zone information for the Eastern
 United States using "RDATE" property. Note that this is only suitable
 for a recurring event that starts on or later than April 6, 1997 at
 03:00:00 EDT (i.e., the earliest effective transition date and time)
 and ends no later than April 7, 1998 02:00:00 EST (i.e., latest valid
 date and time for EST in this scenario). For example, this can be
 used for a recurring event that occurs every Friday, 8am-9:00 AM,
 starting June 1, 1997, ending December 31, 1997.
   BEGIN:VTIMEZONE
   TZID:US-Eastern
   LAST-MODIFIED:19870101T000000Z
   BEGIN:STANDARD
   DTSTART:19971026T020000
   RDATE:19971026T020000
   TZOFFSETFROM:-0400
   TZOFFSETTO:-0500
   TZNAME:EST
   END:STANDARD
   BEGIN:DAYLIGHT
   DTSTART:19971026T020000

Dawson & Stenerson Standards Track [Page 65] RFC 2445 iCalendar November 1998

   RDATE:19970406T020000
   TZOFFSETFROM:-0500
   TZOFFSETTO:-0400
   TZNAME:EDT
   END:DAYLIGHT
   END:VTIMEZONE
 This is a simple example showing the current time zone rules for the
 Eastern United States using a RRULE recurrence pattern. Note that
 there is no effective end date to either of the Standard Time or
 Daylight Time rules. This information would be valid for a recurring
 event starting today and continuing indefinitely.
   BEGIN:VTIMEZONE
   TZID:US-Eastern
   LAST-MODIFIED:19870101T000000Z
   TZURL:http://zones.stds_r_us.net/tz/US-Eastern
   BEGIN:STANDARD
   DTSTART:19671029T020000
   RRULE:FREQ=YEARLY;BYDAY=-1SU;BYMONTH=10
   TZOFFSETFROM:-0400
   TZOFFSETTO:-0500
   TZNAME:EST
   END:STANDARD
   BEGIN:DAYLIGHT
   DTSTART:19870405T020000
   RRULE:FREQ=YEARLY;BYDAY=1SU;BYMONTH=4
   TZOFFSETFROM:-0500
   TZOFFSETTO:-0400
   TZNAME:EDT
   END:DAYLIGHT
   END:VTIMEZONE
 This is an example showing a fictitious set of rules for the Eastern
 United States, where the Daylight Time rule has an effective end date
 (i.e., after that date, Daylight Time is no longer observed).
   BEGIN:VTIMEZONE
   TZID:US--Fictitious-Eastern
   LAST-MODIFIED:19870101T000000Z
   BEGIN:STANDARD
   DTSTART:19671029T020000
   RRULE:FREQ=YEARLY;BYDAY=-1SU;BYMONTH=10
   TZOFFSETFROM:-0400
   TZOFFSETTO:-0500
   TZNAME:EST
   END:STANDARD

Dawson & Stenerson Standards Track [Page 66] RFC 2445 iCalendar November 1998

   BEGIN:DAYLIGHT
   DTSTART:19870405T020000
   RRULE:FREQ=YEARLY;BYDAY=1SU;BYMONTH=4;UNTIL=19980404T070000Z
   TZOFFSETFROM:-0500
   TZOFFSETTO:-0400
   TZNAME:EDT
   END:DAYLIGHT
   END:VTIMEZONE
 This is an example showing a fictitious set of rules for the Eastern
 United States, where the first Daylight Time rule has an effective
 end date. There is a second Daylight Time rule that picks up where
 the other left off.
   BEGIN:VTIMEZONE
   TZID:US--Fictitious-Eastern
   LAST-MODIFIED:19870101T000000Z
   BEGIN:STANDARD
   DTSTART:19671029T020000
   RRULE:FREQ=YEARLY;BYDAY=-1SU;BYMONTH=10
   TZOFFSETFROM:-0400
   TZOFFSETTO:-0500
   TZNAME:EST
   END:STANDARD
   BEGIN:DAYLIGHT
   DTSTART:19870405T020000
   RRULE:FREQ=YEARLY;BYDAY=1SU;BYMONTH=4;UNTIL=19980404T070000Z
   TZOFFSETFROM:-0500
   TZOFFSETTO:-0400
   TZNAME:EDT
   END:DAYLIGHT
   BEGIN:DAYLIGHT
   DTSTART:19990424T020000
   RRULE:FREQ=YEARLY;BYDAY=-1SU;BYMONTH=4
   TZOFFSETFROM:-0500
   TZOFFSETTO:-0400
   TZNAME:EDT
   END:DAYLIGHT
   END:VTIMEZONE

4.6.6 Alarm Component

 Component Name: VALARM
 Purpose: Provide a grouping of component properties that define an
 alarm.

Dawson & Stenerson Standards Track [Page 67] RFC 2445 iCalendar November 1998

 Formal Definition: A "VALARM" calendar component is defined by the
 following notation:
        alarmc     = "BEGIN" ":" "VALARM" CRLF
                     (audioprop / dispprop / emailprop / procprop)
                     "END" ":" "VALARM" CRLF
   audioprop  = 2*(
              ; 'action' and 'trigger' are both REQUIRED,
              ; but MUST NOT occur more than once
              action / trigger /
              ; 'duration' and 'repeat' are both optional,
              ; and MUST NOT occur more than once each,
              ; but if one occurs, so MUST the other
              duration / repeat /
              ; the following is optional,
              ; but MUST NOT occur more than once
              attach /
              ; the following is optional,
              ; and MAY occur more than once
              x-prop
              )
   dispprop   = 3*(
              ; the following are all REQUIRED,
              ; but MUST NOT occur more than once
              action / description / trigger /
              ; 'duration' and 'repeat' are both optional,
              ; and MUST NOT occur more than once each,
              ; but if one occurs, so MUST the other
              duration / repeat /
              ; the following is optional,

Dawson & Stenerson Standards Track [Page 68] RFC 2445 iCalendar November 1998

              ; and MAY occur more than once
  • x-prop
              )
   emailprop  = 5*(
              ; the following are all REQUIRED,
              ; but MUST NOT occur more than once
              action / description / trigger / summary
              ; the following is REQUIRED,
              ; and MAY occur more than once
              attendee /
              ; 'duration' and 'repeat' are both optional,
              ; and MUST NOT occur more than once each,
              ; but if one occurs, so MUST the other
              duration / repeat /
              ; the following are optional,
              ; and MAY occur more than once
              attach / x-prop
              )
   procprop   = 3*(
              ; the following are all REQUIRED,
              ; but MUST NOT occur more than once
              action / attach / trigger /
              ; 'duration' and 'repeat' are both optional,
              ; and MUST NOT occur more than once each,
              ; but if one occurs, so MUST the other
              duration / repeat /

Dawson & Stenerson Standards Track [Page 69] RFC 2445 iCalendar November 1998

              ; 'description' is optional,
              ; and MUST NOT occur more than once
              description /
              ; the following is optional,
              ; and MAY occur more than once
              x-prop
              )
 Description: A "VALARM" calendar component is a grouping of component
 properties that is a reminder or alarm for an event or a to-do. For
 example, it may be used to define a reminder for a pending event or
 an overdue to-do.
 The "VALARM" calendar component MUST include the "ACTION" and
 "TRIGGER" properties. The "ACTION" property further constrains the
 "VALARM" calendar component in the following ways:
 When the action is "AUDIO", the alarm can also include one and only
 one "ATTACH" property, which MUST point to a sound resource, which is
 rendered when the alarm is triggered.
 When the action is "DISPLAY", the alarm MUST also include a
 "DESCRIPTION" property, which contains the text to be displayed when
 the alarm is triggered.
 When the action is "EMAIL", the alarm MUST include a "DESCRIPTION"
 property, which contains the text to be used as the message body, a
 "SUMMARY" property, which contains the text to be used as the message
 subject, and one or more "ATTENDEE" properties, which contain the
 email address of attendees to receive the message. It can also
 include one or more "ATTACH" properties, which are intended to be
 sent as message attachments. When the alarm is triggered, the email
 message is sent.
 When the action is "PROCEDURE", the alarm MUST include one and only
 one "ATTACH" property, which MUST point to a procedure resource,
 which is invoked when the alarm is triggered.
 The "VALARM" calendar component MUST only appear within either a
 "VEVENT" or "VTODO" calendar component. "VALARM" calendar components
 cannot be nested. Multiple mutually independent "VALARM" calendar
 components can be specified for a single "VEVENT" or "VTODO" calendar
 component.

Dawson & Stenerson Standards Track [Page 70] RFC 2445 iCalendar November 1998

 The "TRIGGER" property specifies when the alarm will be triggered.
 The "TRIGGER" property specifies a duration prior to the start of an
 event or a to-do. The "TRIGGER" edge may be explicitly set to be
 relative to the "START" or "END" of the event or to-do with the
 "RELATED" parameter of the "TRIGGER" property. The "TRIGGER" property
 value type can alternatively be set to an absolute calendar date and
 time of day value.
 In an alarm set to trigger on the "START" of an event or to-do, the
 "DTSTART" property MUST be present in the associated event or to-do.
 In an alarm in a "VEVENT" calendar component set to trigger on the
 "END" of the event, either the "DTEND" property MUST be present, or
 the "DTSTART" and "DURATION" properties MUST both be present. In an
 alarm in a "VTODO" calendar component set to trigger on the "END" of
 the to-do, either the "DUE" property MUST be present, or the
 "DTSTART" and "DURATION" properties MUST both be present.
 The alarm can be defined such that it triggers repeatedly. A
 definition of an alarm with a repeating trigger MUST include both the
 "DURATION" and "REPEAT" properties. The "DURATION" property specifies
 the delay period, after which the alarm will repeat. The "REPEAT"
 property specifies the number of additional repetitions that the
 alarm will triggered. This repitition count is in addition to the
 initial triggering of the alarm. Both of these properties MUST be
 present in order to specify a repeating alarm. If one of these two
 properties is absent, then the alarm will not repeat beyond the
 initial trigger.
 The "ACTION" property is used within the "VALARM" calendar component
 to specify the type of action invoked when the alarm is triggered.
 The "VALARM" properties provide enough information for a specific
 action to be invoked. It is typically the responsibility of a
 "Calendar User Agent" (CUA) to deliver the alarm in the specified
 fashion. An "ACTION" property value of AUDIO specifies an alarm that
 causes a sound to be played to alert the user; DISPLAY specifies an
 alarm that causes a text message to be displayed to the user; EMAIL
 specifies an alarm that causes an electronic email message to be
 delivered to one or more email addresses; and PROCEDURE specifies an
 alarm that causes a procedure to be executed. The "ACTION" property
 MUST specify one and only one of these values.
 In an AUDIO alarm, if the optional "ATTACH" property is included, it
 MUST specify an audio sound resource. The intention is that the sound
 will be played as the alarm effect. If an "ATTACH" property is
 specified that does not refer to a sound resource, or if the
 specified sound resource cannot be rendered (because its format is
 unsupported, or because it cannot be retrieved), then the CUA or
 other entity responsible for playing the sound may choose a fallback

Dawson & Stenerson Standards Track [Page 71] RFC 2445 iCalendar November 1998

 action, such as playing a built-in default sound, or playing no sound
 at all.
 In a DISPLAY alarm, the intended alarm effect is for the text value
 of the "DESCRIPTION" property to be displayed to the user.
 In an EMAIL alarm, the intended alarm effect is for an email message
 to be composed and delivered to all the addresses specified by the
 "ATTENDEE" properties in the "VALARM" calendar component. The
 "DESCRIPTION" property of the "VALARM" calendar component MUST be
 used as the body text of the message, and the "SUMMARY" property MUST
 be used as the subject text. Any "ATTACH" properties in the "VALARM"
 calendar component SHOULD be sent as attachments to the message.
 In a PROCEDURE alarm, the "ATTACH" property in the "VALARM" calendar
 component MUST specify a procedure or program that is intended to be
 invoked as the alarm effect. If the procedure or program is in a
 format that cannot be rendered, then no procedure alarm will be
 invoked. If the "DESCRIPTION" property is present, its value
 specifies the argument string to be passed to the procedure or
 program. "Calendar User Agents" that receive an iCalendar object with
 this category of alarm, can disable or allow the "Calendar User" to
 disable, or otherwise ignore this type of alarm. While a very useful
 alarm capability, the PROCEDURE type of alarm SHOULD be treated by
 the "Calendar User Agent" as a potential security risk.
 Example: The following example is for a "VALARM" calendar component
 that specifies an audio alarm that will sound at a precise time and
 repeat 4 more times at 15 minute intervals:
   BEGIN:VALARM
   TRIGGER;VALUE=DATE-TIME:19970317T133000Z
   REPEAT:4
   DURATION:PT15M
   ACTION:AUDIO
   ATTACH;FMTTYPE=audio/basic:ftp://host.com/pub/sounds/bell-01.aud
   END:VALARM
 The following example is for a "VALARM" calendar component that
 specifies a display alarm that will trigger 30 minutes before the
 scheduled start of the event or the due date/time of the to-do it is
 associated with and will repeat 2 more times at 15 minute intervals:
   BEGIN:VALARM
   TRIGGER:-PT30M
   REPEAT:2
   DURATION:PT15M
   ACTION:DISPLAY

Dawson & Stenerson Standards Track [Page 72] RFC 2445 iCalendar November 1998

   DESCRIPTION:Breakfast meeting with executive\n
    team at 8:30 AM EST.
   END:VALARM
 The following example is for a "VALARM" calendar component that
 specifies an email alarm that will trigger 2 days before the
 scheduled due date/time of a to-do it is associated with. It does not
 repeat. The email has a subject, body and attachment link.
   BEGIN:VALARM
   TRIGGER:-P2D
   ACTION:EMAIL
   ATTENDEE:MAILTO:john_doe@host.com
   SUMMARY:*** REMINDER: SEND AGENDA FOR WEEKLY STAFF MEETING ***
   DESCRIPTION:A draft agenda needs to be sent out to the attendees
     to the weekly managers meeting (MGR-LIST). Attached is a
     pointer the document template for the agenda file.
   ATTACH;FMTTYPE=application/binary:http://host.com/templates/agen
    da.doc
   END:VALARM
 The following example is for a "VALARM" calendar component that
 specifies a procedural alarm that will trigger at a precise date/time
 and will repeat 23 more times at one hour intervals. The alarm will
 invoke a procedure file.
   BEGIN:VALARM
   TRIGGER;VALUE=DATE-TIME:19980101T050000Z
   REPEAT:23
   DURATION:PT1H
   ACTION:PROCEDURE
   ATTACH;FMTTYPE=application/binary:ftp://host.com/novo-
    procs/felizano.exe
   END:VALARM

4.7 Calendar Properties

 The Calendar Properties are attributes that apply to the iCalendar
 object, as a whole. These properties do not appear within a calendar
 component. They SHOULD be specified after the "BEGIN:VCALENDAR"
 property and prior to any calendar component.

4.7.1 Calendar Scale

 Property Name: CALSCALE
 Purpose: This property defines the calendar scale used for the
 calendar information specified in the iCalendar object.

Dawson & Stenerson Standards Track [Page 73] RFC 2445 iCalendar November 1998

 Value Type: TEXT
 Property Parameters: Non-standard property parameters can be
 specified on this property.
 Conformance: Property can be specified in an iCalendar object. The
 default value is "GREGORIAN".
 Description: This memo is based on the Gregorian calendar scale. The
 Gregorian calendar scale is assumed if this property is not specified
 in the iCalendar object. It is expected that other calendar scales
 will be defined in other specifications or by future versions of this
 memo.
 Format Definition: The property is defined by the following notation:
   calscale   = "CALSCALE" calparam ":" calvalue CRLF
   calparam   = *(";" xparam)
   calvalue   = "GREGORIAN" / iana-token
 Example: The following is an example of this property:
   CALSCALE:GREGORIAN

4.7.2 Method

 Property Name: METHOD
 Purpose: This property defines the iCalendar object method associated
 with the calendar object.
 Value Type: TEXT
 Property Parameters: Non-standard property parameters can be
 specified on this property.
 Conformance: The property can be specified in an iCalendar object.
 Description: When used in a MIME message entity, the value of this
 property MUST be the same as the Content-Type "method" parameter
 value. This property can only appear once within the iCalendar
 object. If either the "METHOD" property or the Content-Type "method"
 parameter is specified, then the other MUST also be specified.
 No methods are defined by this specification. This is the subject of
 other specifications, such as the iCalendar Transport-independent

Dawson & Stenerson Standards Track [Page 74] RFC 2445 iCalendar November 1998

 Interoperability Protocol (iTIP) defined by [ITIP].
 If this property is not present in the iCalendar object, then a
 scheduling transaction MUST NOT be assumed. In such cases, the
 iCalendar object is merely being used to transport a snapshot of some
 calendar information; without the intention of conveying a scheduling
 semantic.
 Format Definition: The property is defined by the following notation:
   method     = "METHOD" metparam ":" metvalue CRLF
   metparam   = *(";" xparam)
   metvalue   = iana-token
 Example: The following is a hypothetical example of this property to
 convey that the iCalendar object is a request for a meeting:
   METHOD:REQUEST

4.7.3 Product Identifier

 Property Name: PRODID
 Purpose: This property specifies the identifier for the product that
 created the iCalendar object.
 Value Type: TEXT
 Property Parameters: Non-standard property parameters can be
 specified on this property.
 Conformance: The property MUST be specified once in an iCalendar
 object.
 Description: The vendor of the implementation SHOULD assure that this
 is a globally unique identifier; using some technique such as an FPI
 value, as defined in [ISO 9070].
 This property SHOULD not be used to alter the interpretation of an
 iCalendar object beyond the semantics specified in this memo. For
 example, it is not to be used to further the understanding of non-
 standard properties.
 Format Definition: The property is defined by the following notation:
   prodid     = "PRODID" pidparam ":" pidvalue CRLF

Dawson & Stenerson Standards Track [Page 75] RFC 2445 iCalendar November 1998

   pidparam   = *(";" xparam)
   pidvalue   = text
   ;Any text that describes the product and version
   ;and that is generally assured of being unique.
 Example: The following is an example of this property. It does not
 imply that English is the default language.
   PRODID:-//ABC Corporation//NONSGML My Product//EN

4.7.4 Version

 Property Name: VERSION
 Purpose: This property specifies the identifier corresponding to the
 highest version number or the minimum and maximum range of the
 iCalendar specification that is required in order to interpret the
 iCalendar object.
 Value Type: TEXT
 Property Parameters: Non-standard property parameters can be
 specified on this property.
 Conformance: This property MUST be specified by an iCalendar object,
 but MUST only be specified once.
 Description: A value of "2.0" corresponds to this memo.
 Format Definition: The property is defined by the following notation:
   version    = "VERSION" verparam ":" vervalue CRLF
   verparam   = *(";" xparam)
   vervalue   = "2.0"         ;This memo
              / maxver
              / (minver ";" maxver)
   minver     = <A IANA registered iCalendar version identifier>
   ;Minimum iCalendar version needed to parse the iCalendar object
   maxver     = <A IANA registered iCalendar version identifier>
   ;Maximum iCalendar version needed to parse the iCalendar object
 Example: The following is an example of this property:

Dawson & Stenerson Standards Track [Page 76] RFC 2445 iCalendar November 1998

   VERSION:2.0

4.8 Component Properties

 The following properties can appear within calendar components, as
 specified by each component property definition.

4.8.1 Descriptive Component Properties

 The following properties specify descriptive information about
 calendar components.

4.8.1.1 Attachment

 Property Name: ATTACH
 Purpose: The property provides the capability to associate a document
 object with a calendar component.
 Value Type: The default value type for this property is URI. The
 value type can also be set to BINARY to indicate inline binary
 encoded content information.
 Property Parameters: Non-standard, inline encoding, format type and
 value data type property parameters can be specified on this
 property.
 Conformance: The property can be specified in a "VEVENT", "VTODO",
 "VJOURNAL" or "VALARM" calendar components.
 Description: The property can be specified within "VEVENT", "VTODO",
 "VJOURNAL", or "VALARM" calendar components. This property can be
 specified multiple times within an iCalendar object.
 Format Definition: The property is defined by the following notation:
   attach     = "ATTACH" attparam ":" uri  CRLF
   attach     =/ "ATTACH" attparam ";" "ENCODING" "=" "BASE64"
                 ";" "VALUE" "=" "BINARY" ":" binary
   attparam   = *(
              ; the following is optional,
              ; but MUST NOT occur more than once
              (";" fmttypeparam) /

Dawson & Stenerson Standards Track [Page 77] RFC 2445 iCalendar November 1998

              ; the following is optional,
              ; and MAY occur more than once
              (";" xparam)
              )
 Example: The following are examples of this property:
   ATTACH:CID:jsmith.part3.960817T083000.xyzMail@host1.com
   ATTACH;FMTTYPE=application/postscript:ftp://xyzCorp.com/pub/
    reports/r-960812.ps

4.8.1.2 Categories

 Property Name: CATEGORIES
 Purpose: This property defines the categories for a calendar
 component.
 Value Type: TEXT
 Property Parameters: Non-standard and language property parameters
 can be specified on this property.
 Conformance: The property can be specified within "VEVENT", "VTODO"
 or "VJOURNAL" calendar components.
 Description: This property is used to specify categories or subtypes
 of the calendar component. The categories are useful in searching for
 a calendar component of a particular type and category. Within the
 "VEVENT", "VTODO" or "VJOURNAL" calendar components, more than one
 category can be specified as a list of categories separated by the
 COMMA character (US-ASCII decimal 44).
 Format Definition: The property is defined by the following notation:
   categories = "CATEGORIES" catparam ":" text *("," text)
                CRLF
   catparam   = *(
              ; the following is optional,
              ; but MUST NOT occur more than once
              (";" languageparam ) /

Dawson & Stenerson Standards Track [Page 78] RFC 2445 iCalendar November 1998

              ; the following is optional,
              ; and MAY occur more than once
              (";" xparam)
              )
 Example: The following are examples of this property:
   CATEGORIES:APPOINTMENT,EDUCATION
   CATEGORIES:MEETING

4.8.1.3 Classification

 Property Name: CLASS
 Purpose: This property defines the access classification for a
 calendar component.
 Value Type: TEXT
 Property Parameters: Non-standard property parameters can be
 specified on this property.
 Conformance: The property can be specified once in a "VEVENT",
 "VTODO" or "VJOURNAL" calendar components.
 Description: An access classification is only one component of the
 general security system within a calendar application. It provides a
 method of capturing the scope of the access the calendar owner
 intends for information within an individual calendar entry. The
 access classification of an individual iCalendar component is useful
 when measured along with the other security components of a calendar
 system (e.g., calendar user authentication, authorization, access
 rights, access role, etc.). Hence, the semantics of the individual
 access classifications cannot be completely defined by this memo
 alone. Additionally, due to the "blind" nature of most exchange
 processes using this memo, these access classifications cannot serve
 as an enforcement statement for a system receiving an iCalendar
 object. Rather, they provide a method for capturing the intention of
 the calendar owner for the access to the calendar component.
 Format Definition: The property is defined by the following notation:
   class      = "CLASS" classparam ":" classvalue CRLF
   classparam = *(";" xparam)

Dawson & Stenerson Standards Track [Page 79] RFC 2445 iCalendar November 1998

   classvalue = "PUBLIC" / "PRIVATE" / "CONFIDENTIAL" / iana-token
              / x-name
   ;Default is PUBLIC
 Example: The following is an example of this property:
   CLASS:PUBLIC

4.8.1.4 Comment

 Property Name: COMMENT
 Purpose: This property specifies non-processing information intended
 to provide a comment to the calendar user.
 Value Type: TEXT
 Property Parameters: Non-standard, alternate text representation and
 language property parameters can be specified on this property.
 Conformance: This property can be specified in "VEVENT", "VTODO",
 "VJOURNAL", "VTIMEZONE" or "VFREEBUSY" calendar components.
 Description: The property can be specified multiple times.
 Format Definition: The property is defined by the following notation:
   comment    = "COMMENT" commparam ":" text CRLF
   commparam  = *(
              ; the following are optional,
              ; but MUST NOT occur more than once
              (";" altrepparam) / (";" languageparam) /
              ; the following is optional,
              ; and MAY occur more than once
              (";" xparam)
              )
 Example: The following is an example of this property:
   COMMENT:The meeting really needs to include both ourselves
     and the customer. We can't hold this  meeting without them.
     As a matter of fact\, the venue for the meeting ought to be at

Dawson & Stenerson Standards Track [Page 80] RFC 2445 iCalendar November 1998

     their site. - - John
 The data type for this property is TEXT.

4.8.1.5 Description

 Property Name: DESCRIPTION
 Purpose: This property provides a more complete description of the
 calendar component, than that provided by the "SUMMARY" property.
 Value Type: TEXT
 Property Parameters: Non-standard, alternate text representation and
 language property parameters can be specified on this property.
 Conformance: The property can be specified in the "VEVENT", "VTODO",
 "VJOURNAL" or "VALARM" calendar components. The property can be
 specified multiple times only within a "VJOURNAL" calendar component.
 Description: This property is used in the "VEVENT" and "VTODO" to
 capture lengthy textual decriptions associated with the activity.
 This property is used in the "VJOURNAL" calendar component to capture
 one more textual journal entries.
 This property is used in the "VALARM" calendar component to capture
 the display text for a DISPLAY category of alarm, to capture the body
 text for an EMAIL category of alarm and to capture the argument
 string for a PROCEDURE category of alarm.
 Format Definition: The property is defined by the following notation:
   description        = "DESCRIPTION" descparam ":" text CRLF
   descparam  = *(
              ; the following are optional,
              ; but MUST NOT occur more than once
              (";" altrepparam) / (";" languageparam) /
              ; the following is optional,
              ; and MAY occur more than once
              (";" xparam)
              )

Dawson & Stenerson Standards Track [Page 81] RFC 2445 iCalendar November 1998

 Example: The following is an example of the property with formatted
 line breaks in the property value:
   DESCRIPTION:Meeting to provide technical review for "Phoenix"
     design.\n Happy Face Conference Room. Phoenix design team
     MUST attend this meeting.\n RSVP to team leader.
 The following is an example of the property with folding of long
 lines:
   DESCRIPTION:Last draft of the new novel is to be completed
     for the editor's proof today.

4.8.1.6 Geographic Position

 Property Name: GEO
 Purpose: This property specifies information related to the global
 position for the activity specified by a calendar component.
 Value Type: FLOAT. The value MUST be two SEMICOLON separated FLOAT
 values.
 Property Parameters: Non-standard property parameters can be
 specified on this property.
 Conformance: This property can be specified in  "VEVENT" or "VTODO"
 calendar components.
 Description: The property value specifies latitude and longitude, in
 that order (i.e., "LAT LON" ordering). The longitude represents the
 location east or west of the prime meridian as a positive or negative
 real number, respectively. The longitude and latitude values MAY be
 specified up to six decimal places, which will allow for accuracy to
 within one meter of geographical position. Receiving applications
 MUST accept values of this precision and MAY truncate values of
 greater precision.
 Values for latitude and longitude shall be expressed as decimal
 fractions of degrees. Whole degrees of latitude shall be represented
 by a two-digit decimal number ranging from 0 through 90. Whole
 degrees of longitude shall be represented by a decimal number ranging
 from 0 through 180. When a decimal fraction of a degree is specified,
 it shall be separated from the whole number of degrees by a decimal
 point.

Dawson & Stenerson Standards Track [Page 82] RFC 2445 iCalendar November 1998

 Latitudes north of the equator shall be specified by a plus sign (+),
 or by the absence of a minus sign (-), preceding the digits
 designating degrees. Latitudes south of the Equator shall be
 designated by a minus sign (-) preceding the digits designating
 degrees. A point on the Equator shall be assigned to the Northern
 Hemisphere.
 Longitudes east of the prime meridian shall be specified by a plus
 sign (+), or by the absence of a minus sign (-), preceding the digits
 designating degrees. Longitudes west of the meridian shall be
 designated by minus sign (-) preceding the digits designating
 degrees. A point on the prime meridian shall be assigned to the
 Eastern Hemisphere. A point on the 180th meridian shall be assigned
 to the Western Hemisphere. One exception to this last convention is
 permitted. For the special condition of describing a band of latitude
 around the earth, the East Bounding Coordinate data element shall be
 assigned the value +180 (180) degrees.
 Any spatial address with a latitude of +90 (90) or -90 degrees will
 specify the position at the North or South Pole, respectively. The
 component for longitude may have any legal value.
 With the exception of the special condition described above, this
 form is specified in Department of Commerce, 1986, Representation of
 geographic point locations for information interchange (Federal
 Information Processing Standard 70-1):  Washington,  Department of
 Commerce, National Institute of Standards and Technology.
 The simple formula for converting degrees-minutes-seconds into
 decimal degrees is:
   decimal = degrees + minutes/60 + seconds/3600.
 Format Definition: The property is defined by the following notation:
   geo        = "GEO" geoparam ":" geovalue CRLF
   geoparam   = *(";" xparam)
   geovalue   = float ";" float
   ;Latitude and Longitude components
 Example: The following is an example of this property:
   GEO:37.386013;-122.082932

Dawson & Stenerson Standards Track [Page 83] RFC 2445 iCalendar November 1998

4.8.1.7 Location

 Property Name: LOCATION
 Purpose: The property defines the intended venue for the activity
 defined by a calendar component.
 Value Type: TEXT
 Property Parameters: Non-standard, alternate text representation and
 language property parameters can be specified on this property.
 Conformance: This property can be specified in "VEVENT" or "VTODO"
 calendar component.
 Description: Specific venues such as conference or meeting rooms may
 be explicitly specified using this property. An alternate
 representation may be specified that is a URI that points to
 directory information with more structured specification of the
 location. For example, the alternate representation may specify
 either an LDAP URI pointing to an LDAP server entry or a CID URI
 pointing to a MIME body part containing a vCard [RFC 2426] for the
 location.
 Format Definition: The property is defined by the following notation:
   location   = "LOCATION locparam ":" text CRLF
   locparam   = *(
              ; the following are optional,
              ; but MUST NOT occur more than once
              (";" altrepparam) / (";" languageparam) /
              ; the following is optional,
              ; and MAY occur more than once
              (";" xparam)
              )
 Example: The following are some examples of this property:
   LOCATION:Conference Room - F123, Bldg. 002
   LOCATION;ALTREP="http://xyzcorp.com/conf-rooms/f123.vcf":
    Conference Room - F123, Bldg. 002

Dawson & Stenerson Standards Track [Page 84] RFC 2445 iCalendar November 1998

4.8.1.8 Percent Complete

 Property Name: PERCENT-COMPLETE
 Purpose: This property is used by an assignee or delegatee of a to-do
 to convey the percent completion of a to-do to the Organizer.
 Value Type: INTEGER
 Property Parameters: Non-standard property parameters can be
 specified on this property.
 Conformance: This property can be specified in a "VTODO" calendar
 component.
 Description: The property value is a positive integer between zero
 and one hundred. A value of "0" indicates the to-do has not yet been
 started. A value of "100" indicates that the to-do has been
 completed. Integer values in between indicate the percent partially
 complete.
 When a to-do is assigned to multiple individuals, the property value
 indicates the percent complete for that portion of the to-do assigned
 to the assignee or delegatee. For example, if a to-do is assigned to
 both individuals "A" and "B". A reply from "A" with a percent
 complete of "70" indicates that "A" has completed 70% of the to-do
 assigned to them. A reply from "B" with a percent complete of "50"
 indicates "B" has completed 50% of the to-do assigned to them.
 Format Definition: The property is defined by the following notation:
   percent = "PERCENT-COMPLETE" pctparam ":" integer CRLF
   pctparam   = *(";" xparam)
 Example: The following is an example of this property to show 39%
 completion:
   PERCENT-COMPLETE:39

4.8.1.9 Priority

 Property Name: PRIORITY
 Purpose: The property defines the relative priority for a calendar
 component.
 Value Type: INTEGER

Dawson & Stenerson Standards Track [Page 85] RFC 2445 iCalendar November 1998

 Property Parameters: Non-standard property parameters can be
 specified on this property.
 Conformance: The property can be specified in a "VEVENT" or "VTODO"
 calendar component.
 Description: The priority is specified as an integer in the range
 zero to nine. A value of zero (US-ASCII decimal 48) specifies an
 undefined priority. A value of one (US-ASCII decimal 49) is the
 highest priority. A value of two (US-ASCII decimal 50) is the second
 highest priority. Subsequent numbers specify a decreasing ordinal
 priority. A value of nine (US-ASCII decimal 58) is the lowest
 priority.
 A CUA with a three-level priority scheme of "HIGH", "MEDIUM" and
 "LOW" is mapped into this property such that a property value in the
 range of one (US-ASCII decimal 49) to four (US-ASCII decimal 52)
 specifies "HIGH" priority. A value of five (US-ASCII decimal 53) is
 the normal or "MEDIUM" priority. A value in the range of six (US-
 ASCII decimal 54) to nine (US-ASCII decimal 58) is "LOW" priority.
 A CUA with a priority schema of "A1", "A2", "A3", "B1", "B2", ...,
 "C3" is mapped into this property such that a property value of one
 (US-ASCII decimal 49) specifies "A1", a property value of two (US-
 ASCII decimal 50) specifies "A2", a property value of three (US-ASCII
 decimal 51) specifies "A3", and so forth up to a property value of 9
 (US-ASCII decimal 58) specifies "C3".
 Other integer values are reserved for future use.
 Within a "VEVENT" calendar component, this property specifies a
 priority for the event. This property may be useful when more than
 one event is scheduled for a given time period.
 Within a "VTODO" calendar component, this property specified a
 priority for the to-do. This property is useful in prioritizing
 multiple action items for a given time period.
 Format Definition: The property is specified by the following
 notation:
   priority   = "PRIORITY" prioparam ":" privalue CRLF
   ;Default is zero
   prioparam  = *(";" xparam)
   privalue   = integer       ;Must be in the range [0..9]
      ; All other values are reserved for future use

Dawson & Stenerson Standards Track [Page 86] RFC 2445 iCalendar November 1998

 The following is an example of a property with the highest priority:
   PRIORITY:1
 The following is an example of a property with a next highest
 priority:
   PRIORITY:2
 Example: The following is an example of a property with no priority.
 This is equivalent to not specifying the "PRIORITY" property:
   PRIORITY:0

4.8.1.10 Resources

 Property Name: RESOURCES
 Purpose: This property defines the equipment or resources anticipated
 for an activity specified by a calendar entity..
 Value Type: TEXT
 Property Parameters: Non-standard, alternate text representation and
 language property parameters can be specified on this property.
 Conformance: This property can be specified in "VEVENT" or "VTODO"
 calendar component.
 Description: The property value is an arbitrary text. More than one
 resource can be specified as a list of resources separated by the
 COMMA character (US-ASCII decimal 44).
 Format Definition: The property is defined by the following notation:
   resources  = "RESOURCES" resrcparam ":" text *("," text) CRLF
   resrcparam = *(
              ; the following are optional,
              ; but MUST NOT occur more than once
              (";" altrepparam) / (";" languageparam) /
              ; the following is optional,
              ; and MAY occur more than once

Dawson & Stenerson Standards Track [Page 87] RFC 2445 iCalendar November 1998

              (";" xparam)
              )
 Example: The following is an example of this property:
   RESOURCES:EASEL,PROJECTOR,VCR
   RESOURCES;LANGUAGE=fr:1 raton-laveur

4.8.1.11 Status

 Property Name: STATUS
 Purpose: This property defines the overall status or confirmation for
 the calendar component.
 Value Type: TEXT
 Property Parameters: Non-standard property parameters can be
 specified on this property.
 Conformance: This property can be specified in "VEVENT", "VTODO" or
 "VJOURNAL" calendar components.
 Description: In a group scheduled calendar component, the property is
 used by the "Organizer" to provide a confirmation of the event to the
 "Attendees". For example in a "VEVENT" calendar component, the
 "Organizer" can indicate that a meeting is tentative, confirmed or
 cancelled. In a "VTODO" calendar component, the "Organizer" can
 indicate that an action item needs action, is completed, is in
 process or being worked on, or has been cancelled. In a "VJOURNAL"
 calendar component, the "Organizer" can indicate that a journal entry
 is draft, final or has been cancelled or removed.
 Format Definition: The property is defined by the following notation:
   status     = "STATUS" statparam] ":" statvalue CRLF
   statparam  = *(";" xparam)
   statvalue  = "TENTATIVE"           ;Indicates event is
                                      ;tentative.
              / "CONFIRMED"           ;Indicates event is
                                      ;definite.
              / "CANCELLED"           ;Indicates event was
                                      ;cancelled.
      ;Status values for a "VEVENT"

Dawson & Stenerson Standards Track [Page 88] RFC 2445 iCalendar November 1998

   statvalue  =/ "NEEDS-ACTION"       ;Indicates to-do needs action.
              / "COMPLETED"           ;Indicates to-do completed.
              / "IN-PROCESS"          ;Indicates to-do in process of
              / "CANCELLED"           ;Indicates to-do was cancelled.
      ;Status values for "VTODO".
   statvalue  =/ "DRAFT"              ;Indicates journal is draft.
              / "FINAL"               ;Indicates journal is final.
              / "CANCELLED"           ;Indicates journal is removed.
      ;Status values for "VJOURNAL".
 Example: The following is an example of this property for a "VEVENT"
 calendar component:
   STATUS:TENTATIVE
 The following is an example of this property for a "VTODO" calendar
 component:
   STATUS:NEEDS-ACTION
 The following is an example of this property for a "VJOURNAL"
 calendar component:
   STATUS:DRAFT

4.8.1.12 Summary

 Property Name: SUMMARY
 Purpose: This property defines a short summary or subject for the
 calendar component.
 Value Type: TEXT
 Property Parameters: Non-standard, alternate text representation and
 language property parameters can be specified on this property.
 Conformance: The property can be specified in "VEVENT", "VTODO",
 "VJOURNAL" or "VALARM" calendar components.
 Description: This property is used in the "VEVENT", "VTODO" and
 "VJOURNAL" calendar components to capture a short, one line summary
 about the activity or journal entry.
 This property is used in the "VALARM" calendar component to capture
 the subject of an EMAIL category of alarm.

Dawson & Stenerson Standards Track [Page 89] RFC 2445 iCalendar November 1998

 Format Definition: The property is defined by the following notation:
   summary    = "SUMMARY" summparam ":" text CRLF
   summparam  = *(
              ; the following are optional,
              ; but MUST NOT occur more than once
              (";" altrepparam) / (";" languageparam) /
              ; the following is optional,
              ; and MAY occur more than once
              (";" xparam)
              )
 Example: The following is an example of this property:
   SUMMARY:Department Party

4.8.2 Date and Time Component Properties

 The following properties specify date and time related information in
 calendar components.

4.8.2.1 Date/Time Completed

 Property Name: COMPLETED
 Purpose: This property defines the date and time that a to-do was
 actually completed.
 Value Type: DATE-TIME
 Property Parameters: Non-standard property parameters can be
 specified on this property.
 Conformance: The property can be specified in a "VTODO" calendar
 component.
 Description: The date and time MUST be in a UTC format.
 Format Definition: The property is defined by the following notation:
   completed  = "COMPLETED" compparam ":" date-time CRLF

Dawson & Stenerson Standards Track [Page 90] RFC 2445 iCalendar November 1998

   compparam  = *(";" xparam)
 Example: The following is an example of this property:
   COMPLETED:19960401T235959Z

4.8.2.2 Date/Time End

 Property Name: DTEND
 Purpose: This property specifies the date and time that a calendar
 component ends.
 Value Type: The default value type is DATE-TIME. The value type can
 be set to a DATE value type.
 Property Parameters: Non-standard, value data type, time zone
 identifier property parameters can be specified on this property.
 Conformance: This property can be specified in "VEVENT" or
 "VFREEBUSY" calendar components.
 Description: Within the "VEVENT" calendar component, this property
 defines the date and time by which the event ends. The value MUST be
 later in time than the value of the "DTSTART" property.
 Within the "VFREEBUSY" calendar component, this property defines the
 end date and time for the free or busy time information. The time
 MUST be specified in the UTC time format. The value MUST be later in
 time than the value of the "DTSTART" property.
 Format Definition: The property is defined by the following notation:
   dtend      = "DTEND" dtendparam":" dtendval CRLF
   dtendparam = *(
              ; the following are optional,
              ; but MUST NOT occur more than once
              (";" "VALUE" "=" ("DATE-TIME" / "DATE")) /
              (";" tzidparam) /
              ; the following is optional,
              ; and MAY occur more than once

Dawson & Stenerson Standards Track [Page 91] RFC 2445 iCalendar November 1998

              (";" xparam)
              )
   dtendval   = date-time / date
   ;Value MUST match value type
 Example: The following is an example of this property:
   DTEND:19960401T235959Z
   DTEND;VALUE=DATE:19980704

4.8.2.3 Date/Time Due

 Property Name: DUE
 Purpose: This property defines the date and time that a to-do is
 expected to be completed.
 Value Type: The default value type is DATE-TIME. The value type can
 be set to a DATE value type.
 Property Parameters: Non-standard, value data type, time zone
 identifier property parameters can be specified on this property.
 Conformance: The property can be specified once in a "VTODO" calendar
 component.
 Description: The value MUST be a date/time equal to or after the
 DTSTART value, if specified.
 Format Definition: The property is defined by the following notation:
   due        = "DUE" dueparam":" dueval CRLF
   dueparam   = *(
              ; the following are optional,
              ; but MUST NOT occur more than once
              (";" "VALUE" "=" ("DATE-TIME" / "DATE")) /
              (";" tzidparam) /
              ; the following is optional,
              ; and MAY occur more than once

Dawson & Stenerson Standards Track [Page 92] RFC 2445 iCalendar November 1998

  • (";" xparam)
              )
   dueval     = date-time / date
   ;Value MUST match value type
 Example: The following is an example of this property:
   DUE:19980430T235959Z

4.8.2.4 Date/Time Start

 Property Name: DTSTART
 Purpose: This property specifies when the calendar component begins.
 Value Type: The default value type is DATE-TIME. The time value MUST
 be one of the forms defined for the DATE-TIME value type. The value
 type can be set to a DATE value type.
 Property Parameters: Non-standard, value data type, time zone
 identifier property parameters can be specified on this property.
 Conformance: This property can be specified in the "VEVENT", "VTODO",
 "VFREEBUSY", or "VTIMEZONE" calendar components.
 Description: Within the "VEVENT" calendar component, this property
 defines the start date and time for the event. The property is
 REQUIRED in "VEVENT" calendar components. Events can have a start
 date/time but no end date/time. In that case, the event does not take
 up any time.
 Within the "VFREEBUSY" calendar component, this property defines the
 start date and time for the free or busy time information. The time
 MUST be specified in UTC time.
 Within the "VTIMEZONE" calendar component, this property defines the
 effective start date and time for a time zone specification. This
 property is REQUIRED within each STANDARD and DAYLIGHT part included
 in "VTIMEZONE" calendar components and MUST be specified as a local
 DATE-TIME without the "TZID" property parameter.
 Format Definition: The property is defined by the following notation:
   dtstart    = "DTSTART" dtstparam ":" dtstval CRLF

Dawson & Stenerson Standards Track [Page 93] RFC 2445 iCalendar November 1998

   dtstparam  = *(
              ; the following are optional,
              ; but MUST NOT occur more than once
              (";" "VALUE" "=" ("DATE-TIME" / "DATE")) /
              (";" tzidparam) /
              ; the following is optional,
              ; and MAY occur more than once
  • (";" xparam)
              )
   dtstval    = date-time / date
   ;Value MUST match value type
 Example: The following is an example of this property:
   DTSTART:19980118T073000Z

4.8.2.5 Duration

 Property Name: DURATION
 Purpose: The property specifies a positive duration of time.
 Value Type: DURATION
 Property Parameters: Non-standard property parameters can be
 specified on this property.
 Conformance: The property can be specified in "VEVENT", "VTODO",
 "VFREEBUSY" or "VALARM" calendar components.
 Description: In a "VEVENT" calendar component the property may be
 used to specify a duration of the event, instead of an explicit end
 date/time. In a "VTODO" calendar component the property may be used
 to specify a duration for the to-do, instead of an explicit due
 date/time. In a "VFREEBUSY" calendar component the property may be
 used to specify the interval of free time being requested. In a
 "VALARM" calendar component the property may be used to specify the
 delay period prior to repeating an alarm.
 Format Definition: The property is defined by the following notation:

Dawson & Stenerson Standards Track [Page 94] RFC 2445 iCalendar November 1998

   duration   = "DURATION" durparam ":" dur-value CRLF
                ;consisting of a positive duration of time.
   durparam   = *(";" xparam)
 Example: The following is an example of this property that specifies
 an interval of time of 1 hour and zero minutes and zero seconds:
   DURATION:PT1H0M0S
 The following is an example of this property that specifies an
 interval of time of 15 minutes.
   DURATION:PT15M

4.8.2.6 Free/Busy Time

 Property Name: FREEBUSY
 Purpose: The property defines one or more free or busy time
 intervals.
 Value Type: PERIOD. The date and time values MUST be in an UTC time
 format.
 Property Parameters: Non-standard or free/busy time type property
 parameters can be specified on this property.
 Conformance: The property can be specified in a "VFREEBUSY" calendar
 component.
 Property Parameter: "FBTYPE" and non-standard parameters can be
 specified on this property.
 Description: These time periods can be specified as either a start
 and end date-time or a start date-time and duration. The date and
 time MUST be a UTC time format.
 "FREEBUSY" properties within the "VFREEBUSY" calendar component
 SHOULD be sorted in ascending order, based on start time and then end
 time, with the earliest periods first.
 The "FREEBUSY" property can specify more than one value, separated by
 the COMMA character (US-ASCII decimal 44). In such cases, the
 "FREEBUSY" property values SHOULD all be of the same "FBTYPE"
 property parameter type (e.g., all values of a particular "FBTYPE"
 listed together in a single property).

Dawson & Stenerson Standards Track [Page 95] RFC 2445 iCalendar November 1998

 Format Definition: The property is defined by the following notation:
   freebusy   = "FREEBUSY" fbparam ":" fbvalue
                CRLF
   fbparam    = *(
              ; the following is optional,
              ; but MUST NOT occur more than once
              (";" fbtypeparam) /
              ; the following is optional,
              ; and MAY occur more than once
              (";" xparam)
              )
   fbvalue    = period *["," period]
   ;Time value MUST be in the UTC time format.
 Example: The following are some examples of this property:
   FREEBUSY;FBTYPE=BUSY-UNAVAILABLE:19970308T160000Z/PT8H30M
   FREEBUSY;FBTYPE=FREE:19970308T160000Z/PT3H,19970308T200000Z/PT1H
   FREEBUSY;FBTYPE=FREE:19970308T160000Z/PT3H,19970308T200000Z/PT1H,
    19970308T230000Z/19970309T000000Z

4.8.2.7 Time Transparency

 Property Name: TRANSP
 Purpose: This property defines whether an event is transparent or not
 to busy time searches.
 Value Type: TEXT
 Property Parameters: Non-standard property parameters can be
 specified on this property.
 Conformance: This property can be specified once in a "VEVENT"
 calendar component.
 Description: Time Transparency is the characteristic of an event that
 determines whether it appears to consume time on a calendar. Events
 that consume actual time for the individual or resource associated

Dawson & Stenerson Standards Track [Page 96] RFC 2445 iCalendar November 1998

 with the calendar SHOULD be recorded as OPAQUE, allowing them to be
 detected by free-busy time searches. Other events, which do not take
 up the individual's (or resource's) time SHOULD be recorded as
 TRANSPARENT, making them invisible to free-busy time searches.
 Format Definition: The property is specified by the following
 notation:
   transp     = "TRANSP" tranparam ":" transvalue CRLF
   tranparam  = *(";" xparam)
   transvalue = "OPAQUE"      ;Blocks or opaque on busy time searches.
              / "TRANSPARENT" ;Transparent on busy time searches.
      ;Default value is OPAQUE
 Example: The following is an example of this property for an event
 that is transparent or does not block on free/busy time searches:
   TRANSP:TRANSPARENT
 The following is an example of this property for an event that is
 opaque or blocks on free/busy time searches:
   TRANSP:OPAQUE

4.8.3 Time Zone Component Properties

 The following properties specify time zone information in calendar
 components.

4.8.3.1 Time Zone Identifier

 Property Name: TZID
 Purpose: This property specifies the text value that uniquely
 identifies the "VTIMEZONE" calendar component.
 Value Type: TEXT
 Property Parameters: Non-standard property parameters can be
 specified on this property.
 Conformance: This property MUST be specified in a "VTIMEZONE"
 calendar component.

Dawson & Stenerson Standards Track [Page 97] RFC 2445 iCalendar November 1998

 Description: This is the label by which a time zone calendar
 component is referenced by any iCalendar properties whose data type
 is either DATE-TIME or TIME and not intended to specify a UTC or a
 "floating" time. The presence of the SOLIDUS character (US-ASCII
 decimal 47) as a prefix, indicates that this TZID represents an
 unique ID in a globally defined time zone registry (when such
 registry is defined).
      Note: This document does not define a naming convention for time
      zone identifiers. Implementers may want to use the naming
      conventions defined in existing time zone specifications such as
      the public-domain Olson database [TZ]. The specification of
      globally unique time zone identifiers is not addressed by this
      document and is left for future study.
 Format Definition: This property is defined by the following
 notation:
   tzid       = "TZID" tzidpropparam ":" [tzidprefix] text CRLF
   tzidpropparam      = *(";" xparam)
   ;tzidprefix        = "/"
   ; Defined previously. Just listed here for reader convenience.
 Example: The following are examples of non-globally unique time zone
 identifiers:
   TZID:US-Eastern
   TZID:California-Los_Angeles
 The following is an example of a fictitious globally unique time zone
 identifier:
   TZID:/US-New_York-New_York

4.8.3.2 Time Zone Name

 Property Name: TZNAME
 Purpose: This property specifies the customary designation for a time
 zone description.
 Value Type: TEXT
 Property Parameters: Non-standard and language property parameters
 can be specified on this property.

Dawson & Stenerson Standards Track [Page 98] RFC 2445 iCalendar November 1998

 Conformance: This property can be specified in a "VTIMEZONE" calendar
 component.
 Description: This property may be specified in multiple languages; in
 order to provide for different language requirements.
 Format Definition: This property is defined by the following
 notation:
   tzname     = "TZNAME" tznparam ":" text CRLF
   tznparam   = *(
              ; the following is optional,
              ; but MUST NOT occur more than once
              (";" languageparam) /
              ; the following is optional,
              ; and MAY occur more than once
              (";" xparam)
              )
 Example: The following are example of this property:
   TZNAME:EST
 The following is an example of this property when two different
 languages for the time zone name are specified:
   TZNAME;LANGUAGE=en:EST
   TZNAME;LANGUAGE=fr-CA:HNE

4.8.3.3 Time Zone Offset From

 Property Name: TZOFFSETFROM
 Purpose: This property specifies the offset which is in use prior to
 this time zone observance.
 Value Type: UTC-OFFSET
 Property Parameters: Non-standard property parameters can be
 specified on this property.

Dawson & Stenerson Standards Track [Page 99] RFC 2445 iCalendar November 1998

 Conformance: This property MUST be specified in a "VTIMEZONE"
 calendar component.
 Description: This property specifies the offset which is in use prior
 to this time observance. It is used to calculate the absolute time at
 which the transition to a given observance takes place. This property
 MUST only be specified in a "VTIMEZONE" calendar component. A
 "VTIMEZONE" calendar component MUST include this property. The
 property value is a signed numeric indicating the number of hours and
 possibly minutes from UTC. Positive numbers represent time zones east
 of the prime meridian, or ahead of UTC. Negative numbers represent
 time zones west of the prime meridian, or behind UTC.
 Format Definition: The property is defined by the following notation:
   tzoffsetfrom       = "TZOFFSETFROM" frmparam ":" utc-offset
                        CRLF
   frmparam   = *(";" xparam)
 Example: The following are examples of this property:
   TZOFFSETFROM:-0500
   TZOFFSETFROM:+1345

4.8.3.4 Time Zone Offset To

 Property Name: TZOFFSETTO
 Purpose: This property specifies the offset which is in use in this
 time zone observance.
 Value Type: UTC-OFFSET
 Property Parameters: Non-standard property parameters can be
 specified on this property.
 Conformance: This property MUST be specified in a "VTIMEZONE"
 calendar component.
 Description: This property specifies the offset which is in use in
 this time zone observance. It is used to calculate the absolute time
 for the new observance. The property value is a signed numeric
 indicating the number of hours and possibly minutes from UTC.
 Positive numbers represent time zones east of the prime meridian, or
 ahead of UTC. Negative numbers represent time zones west of the prime
 meridian, or behind UTC.

Dawson & Stenerson Standards Track [Page 100] RFC 2445 iCalendar November 1998

 Format Definition: The property is defined by the following notation:
   tzoffsetto = "TZOFFSETTO" toparam ":" utc-offset CRLF
   toparam    = *(";" xparam)
 Example: The following are examples of this property:
   TZOFFSETTO:-0400
   TZOFFSETTO:+1245

4.8.3.5 Time Zone URL

 Property Name: TZURL
 Purpose: The TZURL provides a means for a VTIMEZONE component to
 point to a network location that can be used to retrieve an up-to-
 date version of itself.
 Value Type: URI
 Property Parameters: Non-standard property parameters can be
 specified on this property.
 Conformance: This property can be specified in a "VTIMEZONE" calendar
 component.
 Description: The TZURL provides a means for a VTIMEZONE component to
 point to a network location that can be used to retrieve an up-to-
 date version of itself. This provides a hook to handle changes
 government bodies impose upon time zone definitions. Retrieval of
 this resource results in an iCalendar object containing a single
 VTIMEZONE component and a METHOD property set to PUBLISH.
 Format Definition: The property is defined by the following notation:
   tzurl      = "TZURL" tzurlparam ":" uri CRLF
   tzurlparam = *(";" xparam)
 Example: The following is an example of this property:
   TZURL:http://timezones.r.us.net/tz/US-California-Los_Angeles

Dawson & Stenerson Standards Track [Page 101] RFC 2445 iCalendar November 1998

4.8.4 Relationship Component Properties

 The following properties specify relationship information in calendar
 components.

4.8.4.1 Attendee

 Property Name: ATTENDEE
 Purpose: The property defines an "Attendee" within a calendar
 component.
 Value Type: CAL-ADDRESS
 Property Parameters: Non-standard, language, calendar user type,
 group or list membership, participation role, participation status,
 RSVP expectation, delegatee, delegator, sent by, common name or
 directory entry reference property parameters can be specified on
 this property.
 Conformance: This property MUST be specified in an iCalendar object
 that specifies a group scheduled calendar entity. This property MUST
 NOT be specified in an iCalendar object when publishing the calendar
 information (e.g., NOT in an iCalendar object that specifies the
 publication of a calendar user's busy time, event, to-do or journal).
 This property is not specified in an iCalendar object that specifies
 only a time zone definition or that defines calendar entities that
 are not group scheduled entities, but are entities only on a single
 user's calendar.
 Description: The property MUST only be specified within calendar
 components to specify participants, non-participants and the chair of
 a group scheduled calendar entity. The property is specified within
 an "EMAIL" category of the "VALARM" calendar component to specify an
 email address that is to receive the email type of iCalendar alarm.
 The property parameter CN is for the common or displayable name
 associated with the calendar address; ROLE, for the intended role
 that the attendee will have in the calendar component; PARTSTAT, for
 the status of the attendee's participation; RSVP, for indicating
 whether the favor of a reply is requested; CUTYPE, to indicate the
 type of calendar user; MEMBER, to indicate the groups that the
 attendee belongs to; DELEGATED-TO, to indicate the calendar users
 that the original request was delegated to; and DELEGATED-FROM, to
 indicate whom the request was delegated from; SENT-BY, to indicate
 whom is acting on behalf of the ATTENDEE; and DIR, to indicate the
 URI that points to the directory information corresponding to the
 attendee. These property parameters can be specified on an "ATTENDEE"

Dawson & Stenerson Standards Track [Page 102] RFC 2445 iCalendar November 1998

 property in either a "VEVENT", "VTODO" or "VJOURNAL" calendar
 component. They MUST not be specified in an "ATTENDEE" property in a
 "VFREEBUSY" or "VALARM" calendar component. If the LANGUAGE property
 parameter is specified, the identified language applies to the CN
 parameter.
 A recipient delegated a request MUST inherit the RSVP and ROLE values
 from the attendee that delegated the request to them.
 Multiple attendees can be specified by including multiple "ATTENDEE"
 properties within the calendar component.
 Format Definition: The property is defined by the following notation:
   attendee   = "ATTENDEE" attparam ":" cal-address CRLF
   attparam   = *(
              ; the following are optional,
              ; but MUST NOT occur more than once
              (";" cutypeparam) / (";"memberparam) /
              (";" roleparam) / (";" partstatparam) /
              (";" rsvpparam) / (";" deltoparam) /
              (";" delfromparam) / (";" sentbyparam) /
              (";"cnparam) / (";" dirparam) /
              (";" languageparam) /
              ; the following is optional,
              ; and MAY occur more than once
              (";" xparam)
              )
 Example: The following are examples of this property's use for a to-
 do:
   ORGANIZER:MAILTO:jsmith@host1.com
   ATTENDEE;MEMBER="MAILTO:DEV-GROUP@host2.com":
    MAILTO:joecool@host2.com
   ATTENDEE;DELEGATED-FROM="MAILTO:immud@host3.com":
    MAILTO:ildoit@host1.com
 The following is an example of this property used for specifying
 multiple attendees to an event:

Dawson & Stenerson Standards Track [Page 103] RFC 2445 iCalendar November 1998

   ORGANIZER:MAILTO:jsmith@host1.com
   ATTENDEE;ROLE=REQ-PARTICIPANT;PARTSTAT=TENTATIVE;CN=Henry Cabot
    :MAILTO:hcabot@host2.com
   ATTENDEE;ROLE=REQ-PARTICIPANT;DELEGATED-FROM="MAILTO:bob@host.com"
    ;PARTSTAT=ACCEPTED;CN=Jane Doe:MAILTO:jdoe@host1.com
 The following is an example of this property with a URI to the
 directory information associated with the attendee:
   ATTENDEE;CN=John Smith;DIR="ldap://host.com:6666/o=eDABC%
    20Industries,c=3DUS??(cn=3DBJim%20Dolittle)":MAILTO:jimdo@
    host1.com
 The following is an example of this property with "delegatee" and
 "delegator" information for an event:
   ORGANIZER;CN=John Smith:MAILTO:jsmith@host.com
   ATTENDEE;ROLE=REQ-PARTICIPANT;PARTSTAT=TENTATIVE;DELEGATED-FROM=
    "MAILTO:iamboss@host2.com";CN=Henry Cabot:MAILTO:hcabot@
    host2.com
   ATTENDEE;ROLE=NON-PARTICIPANT;PARTSTAT=DELEGATED;DELEGATED-TO=
    "MAILTO:hcabot@host2.com";CN=The Big Cheese:MAILTO:iamboss
    @host2.com
   ATTENDEE;ROLE=REQ-PARTICIPANT;PARTSTAT=ACCEPTED;CN=Jane Doe
    :MAILTO:jdoe@host1.com
 Example: The following is an example of this property's use when
 another calendar user is acting on behalf of the "Attendee":
   ATTENDEE;SENT-BY=MAILTO:jan_doe@host1.com;CN=John Smith:MAILTO:
    jsmith@host1.com

4.8.4.2 Contact

 Property Name: CONTACT
 Purpose: The property is used to represent contact information or
 alternately a reference to contact information associated with the
 calendar component.
 Value Type: TEXT
 Property Parameters: Non-standard, alternate text representation and
 language property parameters can be specified on this property.
 Conformance: The property can be specified in a "VEVENT", "VTODO",
 "VJOURNAL" or "VFREEBUSY" calendar component.

Dawson & Stenerson Standards Track [Page 104] RFC 2445 iCalendar November 1998

 Description: The property value consists of textual contact
 information. An alternative representation for the property value can
 also be specified that refers to a URI pointing to an alternate form,
 such as a vCard [RFC 2426], for the contact information.
 Format Definition: The property is defined by the following notation:
   contact    = "CONTACT" contparam ":" text CRLF
   contparam  = *(
              ; the following are optional,
              ; but MUST NOT occur more than once
              (";" altrepparam) / (";" languageparam) /
              ; the following is optional,
              ; and MAY occur more than once
              (";" xparam)
              )
 Example: The following is an example of this property referencing
 textual contact information:
   CONTACT:Jim Dolittle\, ABC Industries\, +1-919-555-1234
 The following is an example of this property with an alternate
 representation of a LDAP URI to a directory entry containing the
 contact information:
   CONTACT;ALTREP="ldap://host.com:6666/o=3DABC%20Industries\,
    c=3DUS??(cn=3DBJim%20Dolittle)":Jim Dolittle\, ABC Industries\,
    +1-919-555-1234
 The following is an example of this property with an alternate
 representation of a MIME body part containing the contact
 information, such as a vCard [RFC 2426] embedded in a [MIME-DIR]
 content-type:
   CONTACT;ALTREP="CID=<part3.msg970930T083000SILVER@host.com>":Jim
     Dolittle\, ABC Industries\, +1-919-555-1234
 The following is an example of this property referencing a network
 resource, such as a vCard [RFC 2426] object containing the contact
 information:

Dawson & Stenerson Standards Track [Page 105] RFC 2445 iCalendar November 1998

   CONTACT;ALTREP="http://host.com/pdi/jdoe.vcf":Jim
     Dolittle\, ABC Industries\, +1-919-555-1234

4.8.4.3 Organizer

 Property Name: ORGANIZER
 Purpose: The property defines the organizer for a calendar component.
 Value Type: CAL-ADDRESS
 Property Parameters: Non-standard, language, common name, directory
 entry reference, sent by property parameters can be specified on this
 property.
 Conformance: This property MUST be specified in an iCalendar object
 that specifies a group scheduled calendar entity. This property MUST
 be specified in an iCalendar object that specifies the publication of
 a calendar user's busy time. This property MUST NOT be specified in
 an iCalendar object that specifies only a time zone definition or
 that defines calendar entities that are not group scheduled entities,
 but are entities only on a single user's calendar.
 Description: The property is specified within the "VEVENT", "VTODO",
 "VJOURNAL calendar components to specify the organizer of a group
 scheduled calendar entity. The property is specified within the
 "VFREEBUSY" calendar component to specify the calendar user
 requesting the free or busy time. When publishing a "VFREEBUSY"
 calendar component, the property is used to specify the calendar that
 the published busy time came from.
 The property has the property parameters CN, for specifying the
 common or display name associated with the "Organizer", DIR, for
 specifying a pointer to the directory information associated with the
 "Organizer", SENT-BY, for specifying another calendar user that is
 acting on behalf of the "Organizer". The non-standard parameters may
 also be specified on this property. If the LANGUAGE property
 parameter is specified, the identified language applies to the CN
 parameter value.
 Format Definition: The property is defined by the following notation:
   organizer  = "ORGANIZER" orgparam ":"
                cal-address CRLF
   orgparam   = *(
              ; the following are optional,

Dawson & Stenerson Standards Track [Page 106] RFC 2445 iCalendar November 1998

              ; but MUST NOT occur more than once
              (";" cnparam) / (";" dirparam) / (";" sentbyparam) /
              (";" languageparam) /
              ; the following is optional,
              ; and MAY occur more than once
              (";" xparam)
              )
 Example: The following is an example of this property:
   ORGANIZER;CN=John Smith:MAILTO:jsmith@host1.com
 The following is an example of this property with a pointer to the
 directory information associated with the organizer:
   ORGANIZER;CN=JohnSmith;DIR="ldap://host.com:6666/o=3DDC%20Associ
    ates,c=3DUS??(cn=3DJohn%20Smith)":MAILTO:jsmith@host1.com
 The following is an example of this property used by another calendar
 user who is acting on behalf of the organizer, with responses
 intended to be sent back to the organizer, not the other calendar
 user:
   ORGANIZER;SENT-BY="MAILTO:jane_doe@host.com":
    MAILTO:jsmith@host1.com

4.8.4.4 Recurrence ID

 Property Name: RECURRENCE-ID
 Purpose: This property is used in conjunction with the "UID" and
 "SEQUENCE" property to identify a specific instance of a recurring
 "VEVENT", "VTODO" or "VJOURNAL" calendar component. The property
 value is the effective value of the "DTSTART" property of the
 recurrence instance.
 Value Type: The default value type for this property is DATE-TIME.
 The time format can be any of the valid forms defined for a DATE-TIME
 value type. See DATE-TIME value type definition for specific
 interpretations of the various forms. The value type can be set to
 DATE.

Dawson & Stenerson Standards Track [Page 107] RFC 2445 iCalendar November 1998

 Property Parameters: Non-standard property, value data type, time
 zone identifier and recurrence identifier range parameters can be
 specified on this property.
 Conformance: This property can be specified in an iCalendar object
 containing a recurring calendar component.
 Description: The full range of calendar components specified by a
 recurrence set is referenced by referring to just the "UID" property
 value corresponding to the calendar component. The "RECURRENCE-ID"
 property allows the reference to an individual instance within the
 recurrence set.
 If the value of the "DTSTART" property is a DATE type value, then the
 value MUST be the calendar date for the recurrence instance.
 The date/time value is set to the time when the original recurrence
 instance would occur; meaning that if the intent is to change a
 Friday meeting to Thursday, the date/time is still set to the
 original Friday meeting.
 The "RECURRENCE-ID" property is used in conjunction with the "UID"
 and "SEQUENCE" property to identify a particular instance of a
 recurring event, to-do or journal. For a given pair of "UID" and
 "SEQUENCE" property values, the "RECURRENCE-ID" value for a
 recurrence instance is fixed. When the definition of the recurrence
 set for a calendar component changes, and hence the "SEQUENCE"
 property value changes, the "RECURRENCE-ID" for a given recurrence
 instance might also change.The "RANGE" parameter is used to specify
 the effective range of recurrence instances from the instance
 specified by the "RECURRENCE-ID" property value. The default value
 for the range parameter is the single recurrence instance only. The
 value can also be "THISANDPRIOR" to indicate a range defined by the
 given recurrence instance and all prior instances or the value can be
 "THISANDFUTURE" to indicate a range defined by the given recurrence
 instance and all subsequent instances.
 Format Definition: The property is defined by the following notation:
   recurid    = "RECURRENCE-ID" ridparam ":" ridval CRLF
   ridparam   = *(
              ; the following are optional,
              ; but MUST NOT occur more than once
              (";" "VALUE" "=" ("DATE-TIME" / "DATE)) /
              (";" tzidparam) / (";" rangeparam) /

Dawson & Stenerson Standards Track [Page 108] RFC 2445 iCalendar November 1998

              ; the following is optional,
              ; and MAY occur more than once
              (";" xparam)
              )
   ridval     = date-time / date
   ;Value MUST match value type
 Example: The following are examples of this property:
   RECURRENCE-ID;VALUE=DATE:19960401
   RECURRENCE-ID;RANGE=THISANDFUTURE:19960120T120000Z

4.8.4.5 Related To

 Property Name: RELATED-TO
 Purpose: The property is used to represent a relationship or
 reference between one calendar component and another.
 Value Type: TEXT
 Property Parameters: Non-standard and relationship type property
 parameters can be specified on this property.
 Conformance: The property can be specified one or more times in the
 "VEVENT", "VTODO" or "VJOURNAL" calendar components.
 Description: The property value consists of the persistent, globally
 unique identifier of another calendar component. This value would be
 represented in a calendar component by the "UID" property.
 By default, the property value points to another calendar component
 that has a PARENT relationship to the referencing object. The
 "RELTYPE" property parameter is used to either explicitly state the
 default PARENT relationship type to the referenced calendar component
 or to override the default PARENT relationship type and specify
 either a CHILD or SIBLING relationship. The PARENT relationship
 indicates that the calendar component is a subordinate of the
 referenced calendar component. The CHILD relationship indicates that
 the calendar component is a superior of the referenced calendar
 component. The SIBLING relationship indicates that the calendar
 component is a peer of the referenced calendar component.

Dawson & Stenerson Standards Track [Page 109] RFC 2445 iCalendar November 1998

 Changes to a calendar component referenced by this property can have
 an implicit impact on the related calendar component. For example, if
 a group event changes its start or end date or time, then the
 related, dependent events will need to have their start and end dates
 changed in a corresponding way. Similarly, if a PARENT calendar
 component is canceled or deleted, then there is an implied impact to
 the related CHILD calendar components. This property is intended only
 to provide information on the relationship of calendar components. It
 is up to the target calendar system to maintain any property
 implications of this relationship.
 Format Definition: The property is defined by the following notation:
   related    = "RELATED-TO" [relparam] ":" text CRLF
   relparam   = *(
              ; the following is optional,
              ; but MUST NOT occur more than once
              (";" reltypeparam) /
              ; the following is optional,
              ; and MAY occur more than once
              (";" xparm)
              )
 The following is an example of this property:
   RELATED-TO:<jsmith.part7.19960817T083000.xyzMail@host3.com>
   RELATED-TO:<19960401-080045-4000F192713-0052@host1.com>

4.8.4.6 Uniform Resource Locator

 Property Name: URL
 Purpose: This property defines a Uniform Resource Locator (URL)
 associated with the iCalendar object.
 Value Type: URI
 Property Parameters: Non-standard property parameters can be
 specified on this property.

Dawson & Stenerson Standards Track [Page 110] RFC 2445 iCalendar November 1998

 Conformance: This property can be specified once in the "VEVENT",
 "VTODO", "VJOURNAL" or "VFREEBUSY" calendar components.
 Description: This property may be used in a calendar component to
 convey a location where a more dynamic rendition of the calendar
 information associated with the calendar component can be found. This
 memo does not attempt to standardize the form of the URI, nor the
 format of the resource pointed to by the property value. If the URL
 property and Content-Location MIME header are both specified, they
 MUST point to the same resource.
 Format Definition: The property is defined by the following notation:
   url        = "URL" urlparam ":" uri CRLF
   urlparam   = *(";" xparam)
 Example: The following is an example of this property:
   URL:http://abc.com/pub/calendars/jsmith/mytime.ics

4.8.4.7 Unique Identifier

 Property Name: UID
 Purpose: This property defines the persistent, globally unique
 identifier for the calendar component.
 Value Type: TEXT
 Property Parameters: Non-standard property parameters can be
 specified on this property.
 Conformance: The property MUST be specified in the "VEVENT", "VTODO",
 "VJOURNAL" or "VFREEBUSY" calendar components.
 Description: The UID itself MUST be a globally unique identifier. The
 generator of the identifier MUST guarantee that the identifier is
 unique. There are several algorithms that can be used to accomplish
 this. The identifier is RECOMMENDED to be the identical syntax to the
 [RFC 822] addr-spec. A good method to assure uniqueness is to put the
 domain name or a domain literal IP address of the host on which the
 identifier was created on the right hand side of the "@", and on the
 left hand side, put a combination of the current calendar date and
 time of day (i.e., formatted in as a DATE-TIME value) along with some
 other currently unique (perhaps sequential) identifier available on
 the system (for example, a process id number). Using a date/time
 value on the left hand side and a domain name or domain literal on

Dawson & Stenerson Standards Track [Page 111] RFC 2445 iCalendar November 1998

 the right hand side makes it possible to guarantee uniqueness since
 no two hosts should be using the same domain name or IP address at
 the same time. Though other algorithms will work, it is RECOMMENDED
 that the right hand side contain some domain identifier (either of
 the host itself or otherwise) such that the generator of the message
 identifier can guarantee the uniqueness of the left hand side within
 the scope of that domain.
 This is the method for correlating scheduling messages with the
 referenced "VEVENT", "VTODO", or "VJOURNAL" calendar component.
 The full range of calendar components specified by a recurrence set
 is referenced by referring to just the "UID" property value
 corresponding to the calendar component. The "RECURRENCE-ID" property
 allows the reference to an individual instance within the recurrence
 set.
 This property is an important method for group scheduling
 applications to match requests with later replies, modifications or
 deletion requests. Calendaring and scheduling applications MUST
 generate this property in "VEVENT", "VTODO" and "VJOURNAL" calendar
 components to assure interoperability with other group scheduling
 applications. This identifier is created by the calendar system that
 generates an iCalendar object.
 Implementations MUST be able to receive and persist values of at
 least 255 characters for this property.
 Format Definition: The property is defined by the following notation:
   uid        = "UID" uidparam ":" text CRLF
   uidparam   = *(";" xparam)
 Example: The following is an example of this property:
   UID:19960401T080045Z-4000F192713-0052@host1.com

4.8.5 Recurrence Component Properties

 The following properties specify recurrence information in calendar
 components.

4.8.5.1 Exception Date/Times

 Property Name: EXDATE

Dawson & Stenerson Standards Track [Page 112] RFC 2445 iCalendar November 1998

 Purpose: This property defines the list of date/time exceptions for a
 recurring calendar component.
 Value Type: The default value type for this property is DATE-TIME.
 The value type can be set to DATE.
 Property Parameters: Non-standard, value data type and time zone
 identifier property parameters can be specified on this property.
 Conformance: This property can be specified in an iCalendar object
 that includes a recurring calendar component.
 Description: The exception dates, if specified, are used in computing
 the recurrence set. The recurrence set is the complete set of
 recurrence instances for a calendar component. The recurrence set is
 generated by considering the initial "DTSTART" property along with
 the "RRULE", "RDATE", "EXDATE" and "EXRULE" properties contained
 within the iCalendar object. The "DTSTART" property defines the first
 instance in the recurrence set. Multiple instances of the "RRULE" and
 "EXRULE" properties can also be specified to define more
 sophisticated recurrence sets. The final recurrence set is generated
 by gathering all of the start date-times generated by any of the
 specified "RRULE" and "RDATE" properties, and then excluding any
 start date and times which fall within the union of start date and
 times generated by any specified "EXRULE" and "EXDATE" properties.
 This implies that start date and times within exclusion related
 properties (i.e., "EXDATE" and "EXRULE") take precedence over those
 specified by inclusion properties (i.e., "RDATE" and "RRULE"). Where
 duplicate instances are generated by the "RRULE" and "RDATE"
 properties, only one recurrence is considered. Duplicate instances
 are ignored.
 The "EXDATE" property can be used to exclude the value specified in
 "DTSTART". However, in such cases the original "DTSTART" date MUST
 still be maintained by the calendaring and scheduling system because
 the original "DTSTART" value has inherent usage dependencies by other
 properties such as the "RECURRENCE-ID".
 Format Definition: The property is defined by the following notation:
   exdate     = "EXDATE" exdtparam ":" exdtval *("," exdtval) CRLF
   exdtparam  = *(
              ; the following are optional,
              ; but MUST NOT occur more than once
              (";" "VALUE" "=" ("DATE-TIME" / "DATE")) /

Dawson & Stenerson Standards Track [Page 113] RFC 2445 iCalendar November 1998

              (";" tzidparam) /
              ; the following is optional,
              ; and MAY occur more than once
              (";" xparam)
              )
   exdtval    = date-time / date
   ;Value MUST match value type
 Example: The following is an example of this property:
   EXDATE:19960402T010000Z,19960403T010000Z,19960404T010000Z

4.8.5.2 Exception Rule

 Property Name: EXRULE
 Purpose: This property defines a rule or repeating pattern for an
 exception to a recurrence set.
 Value Type: RECUR
 Property Parameters: Non-standard property parameters can be
 specified on this property.
 Conformance: This property can be specified in "VEVENT", "VTODO" or
 "VJOURNAL" calendar components.
 Description: The exception rule, if specified, is used in computing
 the recurrence set. The recurrence set is the complete set of
 recurrence instances for a calendar component. The recurrence set is
 generated by considering the initial "DTSTART" property along with
 the "RRULE", "RDATE", "EXDATE" and "EXRULE" properties contained
 within the iCalendar object. The "DTSTART" defines the first instance
 in the recurrence set. Multiple instances of the "RRULE" and "EXRULE"
 properties can also be specified to define more sophisticated
 recurrence sets. The final recurrence set is generated by gathering
 all of the start date-times generated by any of the specified "RRULE"
 and "RDATE" properties, and excluding any start date and times which
 fall within the union of start date and times generated by any
 specified "EXRULE" and "EXDATE" properties. This implies that start
 date and times within exclusion related properties (i.e., "EXDATE"
 and "EXRULE") take precedence over those specified by inclusion

Dawson & Stenerson Standards Track [Page 114] RFC 2445 iCalendar November 1998

 properties (i.e., "RDATE" and "RRULE"). Where duplicate instances are
 generated by the "RRULE" and "RDATE" properties, only one recurrence
 is considered. Duplicate instances are ignored.
 The "EXRULE" property can be used to exclude the value specified in
 "DTSTART". However, in such cases the original "DTSTART" date MUST
 still be maintained by the calendaring and scheduling system because
 the original "DTSTART" value has inherent usage dependencies by other
 properties such as the "RECURRENCE-ID".
 Format Definition: The property is defined by the following notation:
   exrule     = "EXRULE" exrparam ":" recur CRLF
   exrparam   = *(";" xparam)
 Example: The following are examples of this property. Except every
 other week, on Tuesday and Thursday for 4 occurrences:
   EXRULE:FREQ=WEEKLY;COUNT=4;INTERVAL=2;BYDAY=TU,TH
 Except daily for 10 occurrences:
   EXRULE:FREQ=DAILY;COUNT=10
 Except yearly in June and July for 8 occurrences:
   EXRULE:FREQ=YEARLY;COUNT=8;BYMONTH=6,7

4.8.5.3 Recurrence Date/Times

 Property Name: RDATE
 Purpose: This property defines the list of date/times for a
 recurrence set.
 Value Type: The default value type for this property is DATE-TIME.
 The value type can be set to DATE or PERIOD.
 Property Parameters: Non-standard, value data type and time zone
 identifier property parameters can be specified on this property.
 Conformance: The property can be specified in "VEVENT", "VTODO",
 "VJOURNAL" or "VTIMEZONE" calendar components.

Dawson & Stenerson Standards Track [Page 115] RFC 2445 iCalendar November 1998

 Description: This property can appear along with the "RRULE" property
 to define an aggregate set of repeating occurrences. When they both
 appear in an iCalendar object, the recurring events are defined by
 the union of occurrences defined by both the "RDATE" and "RRULE".
 The recurrence dates, if specified, are used in computing the
 recurrence set. The recurrence set is the complete set of recurrence
 instances for a calendar component. The recurrence set is generated
 by considering the initial "DTSTART" property along with the "RRULE",
 "RDATE", "EXDATE" and "EXRULE" properties contained within the
 iCalendar object. The "DTSTART" property defines the first instance
 in the recurrence set. Multiple instances of the "RRULE" and "EXRULE"
 properties can also be specified to define more sophisticated
 recurrence sets. The final recurrence set is generated by gathering
 all of the start date/times generated by any of the specified "RRULE"
 and "RDATE" properties, and excluding any start date/times which fall
 within the union of start date/times generated by any specified
 "EXRULE" and "EXDATE" properties. This implies that start date/times
 within exclusion related properties (i.e., "EXDATE" and "EXRULE")
 take precedence over those specified by inclusion properties (i.e.,
 "RDATE" and "RRULE"). Where duplicate instances are generated by the
 "RRULE" and "RDATE" properties, only one recurrence is considered.
 Duplicate instances are ignored.
 Format Definition: The property is defined by the following notation:
   rdate      = "RDATE" rdtparam ":" rdtval *("," rdtval) CRLF
   rdtparam   = *(
              ; the following are optional,
              ; but MUST NOT occur more than once
              (";" "VALUE" "=" ("DATE-TIME" / "DATE" / "PERIOD")) /
              (";" tzidparam) /
              ; the following is optional,
              ; and MAY occur more than once
              (";" xparam)
              )
   rdtval     = date-time / date / period
   ;Value MUST match value type
 Example: The following are examples of this property:

Dawson & Stenerson Standards Track [Page 116] RFC 2445 iCalendar November 1998

   RDATE:19970714T123000Z
   RDATE;TZID=US-EASTERN:19970714T083000
   RDATE;VALUE=PERIOD:19960403T020000Z/19960403T040000Z,
    19960404T010000Z/PT3H
   RDATE;VALUE=DATE:19970101,19970120,19970217,19970421
    19970526,19970704,19970901,19971014,19971128,19971129,19971225

4.8.5.4 Recurrence Rule

 Property Name: RRULE
 Purpose: This property defines a rule or repeating pattern for
 recurring events, to-dos, or time zone definitions.
 Value Type: RECUR
 Property Parameters: Non-standard property parameters can be
 specified on this property.
 Conformance: This property can be specified one or more times in
 recurring "VEVENT", "VTODO" and "VJOURNAL" calendar components. It
 can also be specified once in each STANDARD or DAYLIGHT sub-component
 of the "VTIMEZONE" calendar component.
 Description: The recurrence rule, if specified, is used in computing
 the recurrence set. The recurrence set is the complete set of
 recurrence instances for a calendar component. The recurrence set is
 generated by considering the initial "DTSTART" property along with
 the "RRULE", "RDATE", "EXDATE" and "EXRULE" properties contained
 within the iCalendar object. The "DTSTART" property defines the first
 instance in the recurrence set. Multiple instances of the "RRULE" and
 "EXRULE" properties can also be specified to define more
 sophisticated recurrence sets. The final recurrence set is generated
 by gathering all of the start date/times generated by any of the
 specified "RRULE" and "RDATE" properties, and excluding any start
 date/times which fall within the union of start date/times generated
 by any specified "EXRULE" and "EXDATE" properties. This implies that
 start date/times within exclusion related properties (i.e., "EXDATE"
 and "EXRULE") take precedence over those specified by inclusion
 properties (i.e., "RDATE" and "RRULE"). Where duplicate instances are
 generated by the "RRULE" and "RDATE" properties, only one recurrence
 is considered. Duplicate instances are ignored.

Dawson & Stenerson Standards Track [Page 117] RFC 2445 iCalendar November 1998

 The "DTSTART" and "DTEND" property pair or "DTSTART" and "DURATION"
 property pair, specified within the iCalendar object defines the
 first instance of the recurrence. When used with a recurrence rule,
 the "DTSTART" and "DTEND" properties MUST be specified in local time
 and the appropriate set of "VTIMEZONE" calendar components MUST be
 included. For detail on the usage of the "VTIMEZONE" calendar
 component, see the "VTIMEZONE" calendar component definition.
 Any duration associated with the iCalendar object applies to all
 members of the generated recurrence set. Any modified duration for
 specific recurrences MUST be explicitly specified using the "RDATE"
 property.
 Format Definition: This property is defined by the following
 notation:
   rrule      = "RRULE" rrulparam ":" recur CRLF
   rrulparam  = *(";" xparam)
 Example: All examples assume the Eastern United States time zone.
 Daily for 10 occurrences:
   DTSTART;TZID=US-Eastern:19970902T090000
   RRULE:FREQ=DAILY;COUNT=10
   ==> (1997 9:00 AM EDT)September 2-11
 Daily until December 24, 1997:
   DTSTART;TZID=US-Eastern:19970902T090000
   RRULE:FREQ=DAILY;UNTIL=19971224T000000Z
   ==> (1997 9:00 AM EDT)September 2-30;October 1-25
       (1997 9:00 AM EST)October 26-31;November 1-30;December 1-23
 Every other day - forever:
   DTSTART;TZID=US-Eastern:19970902T090000
   RRULE:FREQ=DAILY;INTERVAL=2
   ==> (1997 9:00 AM EDT)September2,4,6,8...24,26,28,30;
        October 2,4,6...20,22,24
       (1997 9:00 AM EST)October 26,28,30;November 1,3,5,7...25,27,29;
        Dec 1,3,...
 Every 10 days, 5 occurrences:

Dawson & Stenerson Standards Track [Page 118] RFC 2445 iCalendar November 1998

   DTSTART;TZID=US-Eastern:19970902T090000
   RRULE:FREQ=DAILY;INTERVAL=10;COUNT=5
   ==> (1997 9:00 AM EDT)September 2,12,22;October 2,12
 Everyday in January, for 3 years:
   DTSTART;TZID=US-Eastern:19980101T090000
   RRULE:FREQ=YEARLY;UNTIL=20000131T090000Z;
    BYMONTH=1;BYDAY=SU,MO,TU,WE,TH,FR,SA
   or
   RRULE:FREQ=DAILY;UNTIL=20000131T090000Z;BYMONTH=1
   ==> (1998 9:00 AM EDT)January 1-31
       (1999 9:00 AM EDT)January 1-31
       (2000 9:00 AM EDT)January 1-31
 Weekly for 10 occurrences
   DTSTART;TZID=US-Eastern:19970902T090000
   RRULE:FREQ=WEEKLY;COUNT=10
   ==> (1997 9:00 AM EDT)September 2,9,16,23,30;October 7,14,21
       (1997 9:00 AM EST)October 28;November 4
 Weekly until December 24, 1997
   DTSTART;TZID=US-Eastern:19970902T090000
   RRULE:FREQ=WEEKLY;UNTIL=19971224T000000Z
   ==> (1997 9:00 AM EDT)September 2,9,16,23,30;October 7,14,21
       (1997 9:00 AM EST)October 28;November 4,11,18,25;
                         December 2,9,16,23
 Every other week - forever:
   DTSTART;TZID=US-Eastern:19970902T090000
   RRULE:FREQ=WEEKLY;INTERVAL=2;WKST=SU
   ==> (1997 9:00 AM EDT)September 2,16,30;October 14
       (1997 9:00 AM EST)October 28;November 11,25;December 9,23
       (1998 9:00 AM EST)January 6,20;February
   ...
 Weekly on Tuesday and Thursday for 5 weeks:
  DTSTART;TZID=US-Eastern:19970902T090000
  RRULE:FREQ=WEEKLY;UNTIL=19971007T000000Z;WKST=SU;BYDAY=TU,TH
  or

Dawson & Stenerson Standards Track [Page 119] RFC 2445 iCalendar November 1998

  RRULE:FREQ=WEEKLY;COUNT=10;WKST=SU;BYDAY=TU,TH
  ==> (1997 9:00 AM EDT)September 2,4,9,11,16,18,23,25,30;October 2
 Every other week on Monday, Wednesday and Friday until December 24,
 1997, but starting on Tuesday, September 2, 1997:
   DTSTART;TZID=US-Eastern:19970902T090000
   RRULE:FREQ=WEEKLY;INTERVAL=2;UNTIL=19971224T000000Z;WKST=SU;
    BYDAY=MO,WE,FR
   ==> (1997 9:00 AM EDT)September 2,3,5,15,17,19,29;October
   1,3,13,15,17
       (1997 9:00 AM EST)October 27,29,31;November 10,12,14,24,26,28;
                         December 8,10,12,22
 Every other week on Tuesday and Thursday, for 8 occurrences:
   DTSTART;TZID=US-Eastern:19970902T090000
   RRULE:FREQ=WEEKLY;INTERVAL=2;COUNT=8;WKST=SU;BYDAY=TU,TH
   ==> (1997 9:00 AM EDT)September 2,4,16,18,30;October 2,14,16
 Monthly on the 1st Friday for ten occurrences:
   DTSTART;TZID=US-Eastern:19970905T090000
   RRULE:FREQ=MONTHLY;COUNT=10;BYDAY=1FR
   ==> (1997 9:00 AM EDT)September 5;October 3
       (1997 9:00 AM EST)November 7;Dec 5
       (1998 9:00 AM EST)January 2;February 6;March 6;April 3
       (1998 9:00 AM EDT)May 1;June 5
 Monthly on the 1st Friday until December 24, 1997:
   DTSTART;TZID=US-Eastern:19970905T090000
   RRULE:FREQ=MONTHLY;UNTIL=19971224T000000Z;BYDAY=1FR
   ==> (1997 9:00 AM EDT)September 5;October 3
       (1997 9:00 AM EST)November 7;December 5
 Every other month on the 1st and last Sunday of the month for 10
 occurrences:
   DTSTART;TZID=US-Eastern:19970907T090000
   RRULE:FREQ=MONTHLY;INTERVAL=2;COUNT=10;BYDAY=1SU,-1SU
   ==> (1997 9:00 AM EDT)September 7,28
       (1997 9:00 AM EST)November 2,30

Dawson & Stenerson Standards Track [Page 120] RFC 2445 iCalendar November 1998

       (1998 9:00 AM EST)January 4,25;March 1,29
       (1998 9:00 AM EDT)May 3,31
 Monthly on the second to last Monday of the month for 6 months:
   DTSTART;TZID=US-Eastern:19970922T090000
   RRULE:FREQ=MONTHLY;COUNT=6;BYDAY=-2MO
   ==> (1997 9:00 AM EDT)September 22;October 20
       (1997 9:00 AM EST)November 17;December 22
       (1998 9:00 AM EST)January 19;February 16
 Monthly on the third to the last day of the month, forever:
   DTSTART;TZID=US-Eastern:19970928T090000
   RRULE:FREQ=MONTHLY;BYMONTHDAY=-3
   ==> (1997 9:00 AM EDT)September 28
       (1997 9:00 AM EST)October 29;November 28;December 29
       (1998 9:00 AM EST)January 29;February 26
   ...
 Monthly on the 2nd and 15th of the month for 10 occurrences:
   DTSTART;TZID=US-Eastern:19970902T090000
   RRULE:FREQ=MONTHLY;COUNT=10;BYMONTHDAY=2,15
   ==> (1997 9:00 AM EDT)September 2,15;October 2,15
       (1997 9:00 AM EST)November 2,15;December 2,15
       (1998 9:00 AM EST)January 2,15
 Monthly on the first and last day of the month for 10 occurrences:
   DTSTART;TZID=US-Eastern:19970930T090000
   RRULE:FREQ=MONTHLY;COUNT=10;BYMONTHDAY=1,-1
   ==> (1997 9:00 AM EDT)September 30;October 1
       (1997 9:00 AM EST)October 31;November 1,30;December 1,31
       (1998 9:00 AM EST)January 1,31;February 1
 Every 18 months on the 10th thru 15th of the month for 10
 occurrences:
   DTSTART;TZID=US-Eastern:19970910T090000
   RRULE:FREQ=MONTHLY;INTERVAL=18;COUNT=10;BYMONTHDAY=10,11,12,13,14,
    15
   ==> (1997 9:00 AM EDT)September 10,11,12,13,14,15

Dawson & Stenerson Standards Track [Page 121] RFC 2445 iCalendar November 1998

       (1999 9:00 AM EST)March 10,11,12,13
 Every Tuesday, every other month:
   DTSTART;TZID=US-Eastern:19970902T090000
   RRULE:FREQ=MONTHLY;INTERVAL=2;BYDAY=TU
   ==> (1997 9:00 AM EDT)September 2,9,16,23,30
       (1997 9:00 AM EST)November 4,11,18,25
       (1998 9:00 AM EST)January 6,13,20,27;March 3,10,17,24,31
   ...
 Yearly in June and July for 10 occurrences:
   DTSTART;TZID=US-Eastern:19970610T090000
   RRULE:FREQ=YEARLY;COUNT=10;BYMONTH=6,7
   ==> (1997 9:00 AM EDT)June 10;July 10
       (1998 9:00 AM EDT)June 10;July 10
       (1999 9:00 AM EDT)June 10;July 10
       (2000 9:00 AM EDT)June 10;July 10
       (2001 9:00 AM EDT)June 10;July 10
   Note: Since none of the BYDAY, BYMONTHDAY or BYYEARDAY components
   are specified, the day is gotten from DTSTART
 Every other year on January, February, and March for 10 occurrences:
   DTSTART;TZID=US-Eastern:19970310T090000
   RRULE:FREQ=YEARLY;INTERVAL=2;COUNT=10;BYMONTH=1,2,3
   ==> (1997 9:00 AM EST)March 10
       (1999 9:00 AM EST)January 10;February 10;March 10
       (2001 9:00 AM EST)January 10;February 10;March 10
       (2003 9:00 AM EST)January 10;February 10;March 10
 Every 3rd year on the 1st, 100th and 200th day for 10 occurrences:
   DTSTART;TZID=US-Eastern:19970101T090000
   RRULE:FREQ=YEARLY;INTERVAL=3;COUNT=10;BYYEARDAY=1,100,200
   ==> (1997 9:00 AM EST)January 1
       (1997 9:00 AM EDT)April 10;July 19
       (2000 9:00 AM EST)January 1
       (2000 9:00 AM EDT)April 9;July 18
       (2003 9:00 AM EST)January 1
       (2003 9:00 AM EDT)April 10;July 19
       (2006 9:00 AM EST)January 1
 Every 20th Monday of the year, forever:

Dawson & Stenerson Standards Track [Page 122] RFC 2445 iCalendar November 1998

   DTSTART;TZID=US-Eastern:19970519T090000
   RRULE:FREQ=YEARLY;BYDAY=20MO
   ==> (1997 9:00 AM EDT)May 19
       (1998 9:00 AM EDT)May 18
       (1999 9:00 AM EDT)May 17
   ...
 Monday of week number 20 (where the default start of the week is
 Monday), forever:
   DTSTART;TZID=US-Eastern:19970512T090000
   RRULE:FREQ=YEARLY;BYWEEKNO=20;BYDAY=MO
   ==> (1997 9:00 AM EDT)May 12
       (1998 9:00 AM EDT)May 11
       (1999 9:00 AM EDT)May 17
   ...
 Every Thursday in March, forever:
   DTSTART;TZID=US-Eastern:19970313T090000
   RRULE:FREQ=YEARLY;BYMONTH=3;BYDAY=TH
   ==> (1997 9:00 AM EST)March 13,20,27
       (1998 9:00 AM EST)March 5,12,19,26
       (1999 9:00 AM EST)March 4,11,18,25
   ...
 Every Thursday, but only during June, July, and August, forever:
   DTSTART;TZID=US-Eastern:19970605T090000
   RRULE:FREQ=YEARLY;BYDAY=TH;BYMONTH=6,7,8
   ==> (1997 9:00 AM EDT)June 5,12,19,26;July 3,10,17,24,31;
                     August 7,14,21,28
       (1998 9:00 AM EDT)June 4,11,18,25;July 2,9,16,23,30;
                     August 6,13,20,27
       (1999 9:00 AM EDT)June 3,10,17,24;July 1,8,15,22,29;
                     August 5,12,19,26
   ...
 Every Friday the 13th, forever:
   DTSTART;TZID=US-Eastern:19970902T090000
   EXDATE;TZID=US-Eastern:19970902T090000
   RRULE:FREQ=MONTHLY;BYDAY=FR;BYMONTHDAY=13

Dawson & Stenerson Standards Track [Page 123] RFC 2445 iCalendar November 1998

   ==> (1998 9:00 AM EST)February 13;March 13;November 13
       (1999 9:00 AM EDT)August 13
       (2000 9:00 AM EDT)October 13
   ...
 The first Saturday that follows the first Sunday of the month,
  forever:
   DTSTART;TZID=US-Eastern:19970913T090000
   RRULE:FREQ=MONTHLY;BYDAY=SA;BYMONTHDAY=7,8,9,10,11,12,13
   ==> (1997 9:00 AM EDT)September 13;October 11
       (1997 9:00 AM EST)November 8;December 13
       (1998 9:00 AM EST)January 10;February 7;March 7
       (1998 9:00 AM EDT)April 11;May 9;June 13...
   ...
 Every four years, the first Tuesday after a Monday in November,
 forever (U.S. Presidential Election day):
   DTSTART;TZID=US-Eastern:19961105T090000
   RRULE:FREQ=YEARLY;INTERVAL=4;BYMONTH=11;BYDAY=TU;BYMONTHDAY=2,3,4,
    5,6,7,8
   ==> (1996 9:00 AM EST)November 5
       (2000 9:00 AM EST)November 7
       (2004 9:00 AM EST)November 2
   ...
 The 3rd instance into the month of one of Tuesday, Wednesday or
 Thursday, for the next 3 months:
   DTSTART;TZID=US-Eastern:19970904T090000
   RRULE:FREQ=MONTHLY;COUNT=3;BYDAY=TU,WE,TH;BYSETPOS=3
   ==> (1997 9:00 AM EDT)September 4;October 7
       (1997 9:00 AM EST)November 6
 The 2nd to last weekday of the month:
   DTSTART;TZID=US-Eastern:19970929T090000
   RRULE:FREQ=MONTHLY;BYDAY=MO,TU,WE,TH,FR;BYSETPOS=-2
   ==> (1997 9:00 AM EDT)September 29
       (1997 9:00 AM EST)October 30;November 27;December 30
       (1998 9:00 AM EST)January 29;February 26;March 30
   ...

Dawson & Stenerson Standards Track [Page 124] RFC 2445 iCalendar November 1998

 Every 3 hours from 9:00 AM to 5:00 PM on a specific day:
   DTSTART;TZID=US-Eastern:19970902T090000
   RRULE:FREQ=HOURLY;INTERVAL=3;UNTIL=19970902T170000Z
   ==> (September 2, 1997 EDT)09:00,12:00,15:00
 Every 15 minutes for 6 occurrences:
   DTSTART;TZID=US-Eastern:19970902T090000
   RRULE:FREQ=MINUTELY;INTERVAL=15;COUNT=6
   ==> (September 2, 1997 EDT)09:00,09:15,09:30,09:45,10:00,10:15
 Every hour and a half for 4 occurrences:
   DTSTART;TZID=US-Eastern:19970902T090000
   RRULE:FREQ=MINUTELY;INTERVAL=90;COUNT=4
   ==> (September 2, 1997 EDT)09:00,10:30;12:00;13:30
 Every 20 minutes from 9:00 AM to 4:40 PM every day:
   DTSTART;TZID=US-Eastern:19970902T090000
   RRULE:FREQ=DAILY;BYHOUR=9,10,11,12,13,14,15,16;BYMINUTE=0,20,40
   or
   RRULE:FREQ=MINUTELY;INTERVAL=20;BYHOUR=9,10,11,12,13,14,15,16
   ==> (September 2, 1997 EDT)9:00,9:20,9:40,10:00,10:20,
                              ... 16:00,16:20,16:40
       (September 3, 1997 EDT)9:00,9:20,9:40,10:00,10:20,
                             ...16:00,16:20,16:40
   ...
 An example where the days generated makes a difference because of
 WKST:
   DTSTART;TZID=US-Eastern:19970805T090000
   RRULE:FREQ=WEEKLY;INTERVAL=2;COUNT=4;BYDAY=TU,SU;WKST=MO
   ==> (1997 EDT)Aug 5,10,19,24
   changing only WKST from MO to SU, yields different results...
   DTSTART;TZID=US-Eastern:19970805T090000
   RRULE:FREQ=WEEKLY;INTERVAL=2;COUNT=4;BYDAY=TU,SU;WKST=SU
   ==> (1997 EDT)August 5,17,19,31

Dawson & Stenerson Standards Track [Page 125] RFC 2445 iCalendar November 1998

4.8.6 Alarm Component Properties

 The following properties specify alarm information in calendar
 components.

4.8.6.1 Action

 Property Name: ACTION
 Purpose: This property defines the action to be invoked when an alarm
 is triggered.
 Value Type: TEXT
 Property Parameters: Non-standard property parameters can be
 specified on this property.
 Conformance: This property MUST be specified once in a "VALARM"
 calendar component.
 Description: Each "VALARM" calendar component has a particular type
 of action associated with it. This property specifies the type of
 action
 Format Definition: The property is defined by the following notation:
   action     = "ACTION" actionparam ":" actionvalue CRLF
   actionparam        = *(";" xparam)
   actionvalue        = "AUDIO" / "DISPLAY" / "EMAIL" / "PROCEDURE"
                      / iana-token / x-name
 Example: The following are examples of this property in a "VALARM"
 calendar component:
   ACTION:AUDIO
   ACTION:DISPLAY
   ACTION:PROCEDURE

4.8.6.2 Repeat Count

 Property Name: REPEAT
 Purpose: This property defines the number of time the alarm should be
 repeated, after the initial trigger.

Dawson & Stenerson Standards Track [Page 126] RFC 2445 iCalendar November 1998

 Value Type: INTEGER
 Property Parameters: Non-standard property parameters can be
 specified on this property.
 Conformance: This property can be specified in a "VALARM" calendar
 component.
 Description: If the alarm triggers more than once, then this property
 MUST be specified along with the "DURATION" property.
 Format Definition: The property is defined by the following notation:
   repeatcnt  = "REPEAT" repparam ":" integer CRLF
   ;Default is "0", zero.
   repparam   = *(";" xparam)
 Example: The following is an example of this property for an alarm
 that repeats 4 additional times with a 5 minute delay after the
 initial triggering of the alarm:
   REPEAT:4
   DURATION:PT5M

4.8.6.3 Trigger

 Property Name: TRIGGER
 Purpose: This property specifies when an alarm will trigger.
 Value Type: The default value type is DURATION. The value type can be
 set to a DATE-TIME value type, in which case the value MUST specify a
 UTC formatted DATE-TIME value.
 Property Parameters: Non-standard, value data type, time zone
 identifier or trigger relationship property parameters can be
 specified on this property. The trigger relationship property
 parameter MUST only be specified when the value type is DURATION.
 Conformance: This property MUST be specified in the "VALARM" calendar
 component.
 Description: Within the "VALARM" calendar component, this property
 defines when the alarm will trigger. The default value type is
 DURATION, specifying a relative time for the trigger of the alarm.
 The default duration is relative to the start of an event or to-do
 that the alarm is associated with. The duration can be explicitly set

Dawson & Stenerson Standards Track [Page 127] RFC 2445 iCalendar November 1998

 to trigger from either the end or the start of the associated event
 or to-do with the "RELATED" parameter. A value of START will set the
 alarm to trigger off the start of the associated event or to-do. A
 value of END will set the alarm to trigger off the end of the
 associated event or to-do.
 Either a positive or negative duration may be specified for the
 "TRIGGER" property. An alarm with a positive duration is triggered
 after the associated start or end of the event or to-do. An alarm
 with a negative duration is triggered before the associated start or
 end of the event or to-do.
 The "RELATED" property parameter is not valid if the value type of
 the property is set to DATE-TIME (i.e., for an absolute date and time
 alarm trigger). If a value type of DATE-TIME is specified, then the
 property value MUST be specified in the UTC time format. If an
 absolute trigger is specified on an alarm for a recurring event or
 to-do, then the alarm will only trigger for the specified absolute
 date/time, along with any specified repeating instances.
 If the trigger is set relative to START, then the "DTSTART" property
 MUST be present in the associated "VEVENT" or "VTODO" calendar
 component. If an alarm is specified for an event with the trigger set
 relative to the END, then the "DTEND" property or the "DSTART" and
 "DURATION' properties MUST be present in the associated "VEVENT"
 calendar component. If the alarm is specified for a to-do with a
 trigger set relative to the END, then either the "DUE" property or
 the "DSTART" and "DURATION' properties MUST be present in the
 associated "VTODO" calendar component.
 Alarms specified in an event or to-do which is defined in terms of a
 DATE value type will be triggered relative to 00:00:00 UTC on the
 specified date. For example, if "DTSTART:19980205, then the duration
 trigger will be relative to19980205T000000Z.
 Format Definition: The property is defined by the following notation:
   trigger    = "TRIGGER" (trigrel / trigabs)
   trigrel    = *(
              ; the following are optional,
              ; but MUST NOT occur more than once
                (";" "VALUE" "=" "DURATION") /
                (";" trigrelparam) /
              ; the following is optional,

Dawson & Stenerson Standards Track [Page 128] RFC 2445 iCalendar November 1998

              ; and MAY occur more than once
                (";" xparam)
                ) ":"  dur-value
   trigabs    = 1*(
              ; the following is REQUIRED,
              ; but MUST NOT occur more than once
                (";" "VALUE" "=" "DATE-TIME") /
              ; the following is optional,
              ; and MAY occur more than once
                (";" xparam)
                ) ":" date-time
 Example: A trigger set 15 minutes prior to the start of the event or
 to-do.
   TRIGGER:-P15M
 A trigger set 5 minutes after the end of the event or to-do.
   TRIGGER;RELATED=END:P5M
 A trigger set to an absolute date/time.
   TRIGGER;VALUE=DATE-TIME:19980101T050000Z

4.8.7 Change Management Component Properties

 The following properties specify change management information in
 calendar components.

4.8.7.1 Date/Time Created

 Property Name: CREATED
 Purpose: This property specifies the date and time that the calendar
 information was created by the calendar user agent in the calendar
 store.
      Note: This is analogous to the creation date and time for a file
      in the file system.

Dawson & Stenerson Standards Track [Page 129] RFC 2445 iCalendar November 1998

 Value Type: DATE-TIME
 Property Parameters: Non-standard property parameters can be
 specified on this property.
 Conformance: The property can be specified once in "VEVENT", "VTODO"
 or "VJOURNAL" calendar components.
 Description: The date and time is a UTC value.
 Format Definition: The property is defined by the following notation:
   created    = "CREATED" creaparam ":" date-time CRLF
   creaparam  = *(";" xparam)
 Example: The following is an example of this property:
   CREATED:19960329T133000Z

4.8.7.2 Date/Time Stamp

 Property Name: DTSTAMP
 Purpose: The property indicates the date/time that the instance of
 the iCalendar object was created.
 Value Type: DATE-TIME
 Property Parameters: Non-standard property parameters can be
 specified on this property.
 Conformance: This property MUST be included in the "VEVENT", "VTODO",
 "VJOURNAL" or "VFREEBUSY" calendar components.
 Description: The value MUST be specified in the UTC time format.
 This property is also useful to protocols such as [IMIP] that have
 inherent latency issues with the delivery of content. This property
 will assist in the proper sequencing of messages containing iCalendar
 objects.
 This property is different than the "CREATED" and "LAST-MODIFIED"
 properties. These two properties are used to specify when the
 particular calendar data in the calendar store was created and last
 modified. This is different than when the iCalendar object
 representation of the calendar service information was created or
 last modified.

Dawson & Stenerson Standards Track [Page 130] RFC 2445 iCalendar November 1998

 Format Definition: The property is defined by the following notation:
   dtstamp    = "DTSTAMP" stmparam ":" date-time CRLF
   stmparam   = *(";" xparam)
 Example:
   DTSTAMP:19971210T080000Z

4.8.7.3 Last Modified

 Property Name: LAST-MODIFIED
 Purpose: The property specifies the date and time that the
 information associated with the calendar component was last revised
 in the calendar store.
      Note: This is analogous to the modification date and time for a
      file in the file system.
 Value Type: DATE-TIME
 Property Parameters: Non-standard property parameters can be
 specified on this property.
 Conformance: This property can be specified in the "EVENT", "VTODO",
 "VJOURNAL" or "VTIMEZONE" calendar components.
 Description: The property value MUST be specified in the UTC time
 format.
 Format Definition: The property is defined by the following notation:
   last-mod   = "LAST-MODIFIED" lstparam ":" date-time CRLF
   lstparam   = *(";" xparam)
 Example: The following is are examples of this property:
   LAST-MODIFIED:19960817T133000Z

4.8.7.4 Sequence Number

 Property Name: SEQUENCE
 Purpose: This property defines the revision sequence number of the
 calendar component within a sequence of revisions.

Dawson & Stenerson Standards Track [Page 131] RFC 2445 iCalendar November 1998

 Value Type: integer
 Property Parameters: Non-standard property parameters can be
 specified on this property.
 Conformance: The property can be specified in "VEVENT", "VTODO" or
 "VJOURNAL" calendar component.
 Description: When a calendar component is created, its sequence
 number is zero (US-ASCII decimal 48). It is monotonically incremented
 by the "Organizer's" CUA each time the "Organizer" makes a
 significant revision to the calendar component. When the "Organizer"
 makes changes to one of the following properties, the sequence number
 MUST be incremented:
   .  "DTSTART"
   .  "DTEND"
   .  "DUE"
   .  "RDATE"
   .  "RRULE"
   .  "EXDATE"
   .  "EXRULE"
   .  "STATUS"
 In addition, changes made by the "Organizer" to other properties can
 also force the sequence number to be incremented. The "Organizer" CUA
 MUST increment the sequence number when ever it makes changes to
 properties in the calendar component that the "Organizer" deems will
 jeopardize the validity of the participation status of the
 "Attendees". For example, changing the location of a meeting from one
 locale to another distant locale could effectively impact the
 participation status of the "Attendees".
 The "Organizer" includes this property in an iCalendar object that it
 sends to an "Attendee" to specify the current version of the calendar
 component.
 The "Attendee" includes this property in an iCalendar object that it
 sends to the "Organizer" to specify the version of the calendar
 component that the "Attendee" is referring to.

Dawson & Stenerson Standards Track [Page 132] RFC 2445 iCalendar November 1998

 A change to the sequence number is not the mechanism that an
 "Organizer" uses to request a response from the "Attendees". The
 "RSVP" parameter on the "ATTENDEE" property is used by the
 "Organizer" to indicate that a response from the "Attendees" is
 requested.
 Format Definition: This property is defined by the following
 notation:
   seq = "SEQUENCE" seqparam ":" integer CRLF
   ; Default is "0"
   seqparam   = *(";" xparam)
 Example: The following is an example of this property for a calendar
 component that was just created by the "Organizer".
   SEQUENCE:0
 The following is an example of this property for a calendar component
 that has been revised two different times by the "Organizer".
   SEQUENCE:2

4.8.8 Miscellaneous Component Properties

 The following properties specify information about a number of
 miscellaneous features of calendar components.

4.8.8.1 Non-standard Properties

 Property Name: Any property name with a "X-" prefix
 Purpose: This class of property provides a framework for defining
 non-standard properties.
 Value Type: TEXT
 Property Parameters: Non-standard and language property parameters
 can be specified on this property.
 Conformance: This property can be specified in any calendar
 component.
 Description: The MIME Calendaring and Scheduling Content Type
 provides a "standard mechanism for doing non-standard things". This
 extension support is provided for implementers to "push the envelope"
 on the existing version of the memo. Extension properties are

Dawson & Stenerson Standards Track [Page 133] RFC 2445 iCalendar November 1998

 specified by property and/or property parameter names that have the
 prefix text of "X-" (the two character sequence: LATIN CAPITAL LETTER
 X character followed by the HYPEN-MINUS character). It is recommended
 that vendors concatenate onto this sentinel another short prefix text
 to identify the vendor. This will facilitate readability of the
 extensions and minimize possible collision of names between different
 vendors. User agents that support this content type are expected to
 be able to parse the extension properties and property parameters but
 can ignore them.
 At present, there is no registration authority for names of extension
 properties and property parameters. The data type for this property
 is TEXT. Optionally, the data type can be any of the other valid data
 types.
 Format Definition: The property is defined by the following notation:
   x-prop     = x-name *(";" xparam) [";" languageparam] ":" text CRLF
      ; Lines longer than 75 octets should be folded
 Example: The following might be the ABC vendor's extension for an
 audio-clip form of subject property:
   X-ABC-MMSUBJ;X-ABC-MMSUBJTYPE=wave:http://load.noise.org/mysubj.wav

4.8.8.2 Request Status

 Property Name: REQUEST-STATUS
 Purpose: This property defines the status code returned for a
 scheduling request.
 Value Type: TEXT
 Property Parameters: Non-standard and language property parameters
 can be specified on this property.
 Conformance: The property can be specified in "VEVENT", "VTODO",
 "VJOURNAL" or "VFREEBUSY" calendar component.
 Description: This property is used to return status code information
 related to the processing of an associated iCalendar object. The data
 type for this property is TEXT.
 The value consists of a short return status component, a longer
 return status description component, and optionally a status-specific
 data component. The components of the value are separated by the
 SEMICOLON character (US-ASCII decimal 59).

Dawson & Stenerson Standards Track [Page 134] RFC 2445 iCalendar November 1998

 The short return status is a PERIOD character (US-ASCII decimal 46)
 separated 3-tuple of integers. For example, "3.1.1". The successive
 levels of integers provide for a successive level of status code
 granularity.
 The following are initial classes for the return status code.
 Individual iCalendar object methods will define specific return
 status codes for these classes. In addition, other classes for the
 return status code may be defined using the registration process
 defined later in this memo.
   |==============+===============================================|
   | Short Return | Longer Return Status Description              |
   | Status Code  |                                               |
   |==============+===============================================|
   |    1.xx      | Preliminary success. This class of status     |
   |              | of status code indicates that the request has |
   |              | request has been initially processed but that |
   |              | completion is pending.                        |
   |==============+===============================================|
   |    2.xx      | Successful. This class of status code         |
   |              | indicates that the request was completed      |
   |              | successfuly. However, the exact status code   |
   |              | can indicate that a fallback has been taken.  |
   |==============+===============================================|
   |    3.xx      | Client Error. This class of status code       |
   |              | indicates that the request was not successful.|
   |              | The error is the result of either a syntax or |
   |              | a semantic error in the client formatted      |
   |              | request. Request should not be retried until  |
   |              | the condition in the request is corrected.    |
   |==============+===============================================|
   |    4.xx      | Scheduling Error. This class of status code   |
   |              | indicates that the request was not successful.|
   |              | Some sort of error occurred within the        |
   |              | calendaring and scheduling service, not       |
   |              | directly related to the request itself.       |
   |==============+===============================================|
 Format Definition: The property is defined by the following notation:
   rstatus    = "REQUEST-STATUS" rstatparam ":"
                statcode ";" statdesc [";" extdata]
   rstatparam = *(
              ; the following is optional,
              ; but MUST NOT occur more than once

Dawson & Stenerson Standards Track [Page 135] RFC 2445 iCalendar November 1998

              (";" languageparm) /
              ; the following is optional,
              ; and MAY occur more than once
              (";" xparam)
              )
   statcode   = 1*DIGIT *("." 1*DIGIT)
   ;Hierarchical, numeric return status code
   statdesc   = text
   ;Textual status description
   extdata    = text
   ;Textual exception data. For example, the offending property
   ;name and value or complete property line.
 Example: The following are some possible examples of this property.
 The COMMA and SEMICOLON separator characters in the property value
 are BACKSLASH character escaped because they appear in a  text value.
   REQUEST-STATUS:2.0;Success
   REQUEST-STATUS:3.1;Invalid property value;DTSTART:96-Apr-01
   REQUEST-STATUS:2.8; Success\, repeating event ignored. Scheduled
    as a single event.;RRULE:FREQ=WEEKLY\;INTERVAL=2
   REQUEST-STATUS:4.1;Event conflict. Date/time is busy.
   REQUEST-STATUS:3.7;Invalid calendar user;ATTENDEE:
    MAILTO:jsmith@host.com

5 iCalendar Object Examples

 The following examples are provided as an informational source of
 illustrative iCalendar objects consistent with this content type.
 The following example specifies a three-day conference that begins at
 8:00 AM EDT, September 18, 1996 and end at 6:00 PM EDT, September 20,
 1996.
   BEGIN:VCALENDAR PRODID:-//xyz Corp//NONSGML PDA Calendar Verson
   1.0//EN VERSION:2.0 BEGIN:VEVENT DTSTAMP:19960704T120000Z
   UID:uid1@host.com ORGANIZER:MAILTO:jsmith@host.com
   DTSTART:19960918T143000Z DTEND:19960920T220000Z STATUS:CONFIRMED

Dawson & Stenerson Standards Track [Page 136] RFC 2445 iCalendar November 1998

   CATEGORIES:CONFERENCE SUMMARY:Networld+Interop Conference
   DESCRIPTION:Networld+Interop Conference
     and Exhibit\nAtlanta World Congress Center\n
    Atlanta, Georgia END:VEVENT END:VCALENDAR
 The following example specifies a group scheduled meeting that begin
 at 8:30 AM EST on March 12, 1998 and end at 9:30 AM EST on March 12,
 1998. The "Organizer" has scheduled the meeting with one or more
 calendar users in a group. A time zone specification for Eastern
 United States has been specified.
   BEGIN:VCALENDAR
   PRODID:-//RDU Software//NONSGML HandCal//EN
   VERSION:2.0
   BEGIN:VTIMEZONE
   TZID:US-Eastern
   BEGIN:STANDARD
   DTSTART:19981025T020000
   RDATE:19981025T020000
   TZOFFSETFROM:-0400
   TZOFFSETTO:-0500
   TZNAME:EST
   END:STANDARD
   BEGIN:DAYLIGHT
   DTSTART:19990404T020000
   RDATE:19990404T020000
   TZOFFSETFROM:-0500
   TZOFFSETTO:-0400
   TZNAME:EDT
   END:DAYLIGHT
   END:VTIMEZONE
   BEGIN:VEVENT
   DTSTAMP:19980309T231000Z
   UID:guid-1.host1.com
   ORGANIZER;ROLE=CHAIR:MAILTO:mrbig@host.com
   ATTENDEE;RSVP=TRUE;ROLE=REQ-PARTICIPANT;CUTYPE=GROUP:
    MAILTO:employee-A@host.com
   DESCRIPTION:Project XYZ Review Meeting
   CATEGORIES:MEETING
   CLASS:PUBLIC
   CREATED:19980309T130000Z
   SUMMARY:XYZ Project Review
   DTSTART;TZID=US-Eastern:19980312T083000
   DTEND;TZID=US-Eastern:19980312T093000
   LOCATION:1CP Conference Room 4350
   END:VEVENT
   END:VCALENDAR

Dawson & Stenerson Standards Track [Page 137] RFC 2445 iCalendar November 1998

 The following is an example of an iCalendar object passed in a MIME
 message with a single body part consisting of a "text/calendar"
 Content Type.
   TO:jsmith@host1.com
   FROM:jdoe@host1.com
   MIME-VERSION:1.0
   MESSAGE-ID:<id3@host1.com>
   CONTENT-TYPE:text/calendar
   BEGIN:VCALENDAR
   METHOD:xyz
   VERSION:2.0
   PRODID:-//ABC Corporation//NONSGML My Product//EN
   BEGIN:VEVENT
   DTSTAMP:19970324T1200Z
   SEQUENCE:0
   UID:uid3@host1.com
   ORGANIZER:MAILTO:jdoe@host1.com
   ATTENDEE;RSVP=TRUE:MAILTO:jsmith@host1.com
   DTSTART:19970324T123000Z
   DTEND:19970324T210000Z
   CATEGORIES:MEETING,PROJECT
   CLASS:PUBLIC
   SUMMARY:Calendaring Interoperability Planning Meeting
   DESCRIPTION:Discuss how we can test c&s interoperability\n
    using iCalendar and other IETF standards.
   LOCATION:LDB Lobby
   ATTACH;FMTTYPE=application/postscript:ftp://xyzCorp.com/pub/
    conf/bkgrnd.ps
   END:VEVENT
   END:VCALENDAR
 The following is an example of a to-do due on April 15, 1998. An
 audio alarm has been specified to remind the calendar user at noon,
 the day before the to-do is expected to be completed and repeat
 hourly, four additional times. The to-do definition has been modified
 twice since it was initially created.
   BEGIN:VCALENDAR
   VERSION:2.0
   PRODID:-//ABC Corporation//NONSGML My Product//EN
   BEGIN:VTODO
   DTSTAMP:19980130T134500Z
   SEQUENCE:2
   UID:uid4@host1.com
   ORGANIZER:MAILTO:unclesam@us.gov
   ATTENDEE;PARTSTAT=ACCEPTED:MAILTO:jqpublic@host.com

Dawson & Stenerson Standards Track [Page 138] RFC 2445 iCalendar November 1998

   DUE:19980415T235959
   STATUS:NEEDS-ACTION
   SUMMARY:Submit Income Taxes
   BEGIN:VALARM
   ACTION:AUDIO
   TRIGGER:19980403T120000
   ATTACH;FMTTYPE=audio/basic:http://host.com/pub/audio-
    files/ssbanner.aud
   REPEAT:4
   DURATION:PT1H
   END:VALARM
   END:VTODO
   END:VCALENDAR
 The following is an example of a journal entry.
   BEGIN:VCALENDAR
   VERSION:2.0
   PRODID:-//ABC Corporation//NONSGML My Product//EN
   BEGIN:VJOURNAL
   DTSTAMP:19970324T120000Z
   UID:uid5@host1.com
   ORGANIZER:MAILTO:jsmith@host.com
   STATUS:DRAFT
   CLASS:PUBLIC
   CATEGORY:Project Report, XYZ, Weekly Meeting
   DESCRIPTION:Project xyz Review Meeting Minutes\n
    Agenda\n1. Review of project version 1.0 requirements.\n2.
   Definition
    of project processes.\n3. Review of project schedule.\n
    Participants: John Smith, Jane Doe, Jim Dandy\n-It was
     decided that the requirements need to be signed off by
     product marketing.\n-Project processes were accepted.\n
    -Project schedule needs to account for scheduled holidays
     and employee vacation time. Check with HR for specific
     dates.\n-New schedule will be distributed by Friday.\n-
    Next weeks meeting is cancelled. No meeting until 3/23.
   END:VJOURNAL
   END:VCALENDAR
 The following is an example of published busy time information. The
 iCalendar object might be placed in the network resource
 www.host.com/calendar/busytime/jsmith.ifb.
   BEGIN:VCALENDAR
   VERSION:2.0
   PRODID:-//RDU Software//NONSGML HandCal//EN
   BEGIN:VFREEBUSY

Dawson & Stenerson Standards Track [Page 139] RFC 2445 iCalendar November 1998

   ORGANIZER:MAILTO:jsmith@host.com
   DTSTART:19980313T141711Z
   DTEND:19980410T141711Z
   FREEBUSY:19980314T233000Z/19980315T003000Z
   FREEBUSY:19980316T153000Z/19980316T163000Z
   FREEBUSY:19980318T030000Z/19980318T040000Z
   URL:http://www.host.com/calendar/busytime/jsmith.ifb
   END:VFREEBUSY
   END:VCALENDAR

6 Recommended Practices

 These recommended practices should be followed in order to assure
 consistent handling of the following cases for an iCalendar object.
 1.  Content lines longer than 75 octets SHOULD be folded.
 2.  A calendar entry with a "DTSTART" property but no "DTEND"
     property does not take up any time. It is intended to represent
     an event that is associated with a given calendar date and time
     of day, such as an anniversary. Since the event does not take up
     any time, it MUST NOT be used to record busy time no matter what
     the value for the "TRANSP" property.
 3.  When the "DTSTART" and "DTEND", for "VEVENT", "VJOURNAL" and
     "VFREEBUSY" calendar components, and "DTSTART" and "DUE", for
     "VTODO" calendar components, have the same value data type (e.g.,
     DATE-TIME), they SHOULD specify values in the same time format
     (e.g., UTC time format).
 4.  When the combination of the "RRULE" and "RDATE" properties on an
     iCalendar object produces multiple instances having the same
     start date/time, they should be collapsed to, and considered as,
     a single instance.
 5.  When a calendar user receives multiple requests for the same
     calendar component (e.g., REQUEST for a "VEVENT" calendar
     component) as a result of being on multiple mailing lists
     specified by "ATTENDEE" properties in the request, they SHOULD
     respond to only one of the requests. The calendar user SHOULD
     also specify (using the "MEMBER" parameter of the "ATTENDEE"
     property) which mailing list they are a member of.
 6.  An implementation can truncate a "SUMMARY" property value to 255
     characters.

Dawson & Stenerson Standards Track [Page 140] RFC 2445 iCalendar November 1998

 7.  If seconds of the minute are not supported by an implementation,
     then a value of "00" SHOULD be specified for the seconds
     component in a time value.
 8.  If the value type parameter (VALUE=) contains an unknown value
     type, it SHOULD be treated as TEXT.
 9.  TZURL values SHOULD NOT be specified as a FILE URI type. This URI
     form can be useful within an organization, but is problematic in
     the Internet.
 10.  Some possible English values for CATEGORIES property include
      "ANNIVERSARY", "APPOINTMENT", "BUSINESS", "EDUCATION",
      "HOLIDAY", "MEETING", "MISCELLANEOUS", "NON-WORKING HOURS", "NOT
      IN OFFICE", "PERSONAL", "PHONE CALL", "SICK DAY", "SPECIAL
      OCCASION", "TRAVEL", "VACATION". Categories can be specified in
      any registered language.
 11.  Some possible English values for RESOURCES property include
      "CATERING", "CHAIRS", "COMPUTER PROJECTOR", "EASEL", "OVERHEAD
      PROJECTOR", "SPEAKER PHONE", "TABLE", "TV", "VCR", "VIDEO
      PHONE", "VEHICLE". Resources can be specified in any registered
      language.

7 Registration of Content Type Elements

 This section provides the process for registration of MIME
 Calendaring and Scheduling Content Type iCalendar object methods and
 new or modified properties.

7.1 Registration of New and Modified iCalendar Object Methods

 New MIME Calendaring and Scheduling Content Type iCalendar object
 methods are registered by the publication of an IETF Request for
 Comments (RFC). Changes to an iCalendar object method are registered
 by the publication of a revision of the RFC defining the method.

7.2 Registration of New Properties

 This section defines procedures by which new properties or enumerated
 property values for the MIME Calendaring and Scheduling Content Type
 can be registered with the IANA. Non-IANA properties can be used by
 bilateral agreement, provided the associated properties names follow
 the "X-" convention.
 The procedures defined here are designed to allow public comment and
 review of new properties, while posing only a small impediment to the
 definition of new properties.

Dawson & Stenerson Standards Track [Page 141] RFC 2445 iCalendar November 1998

 Registration of a new property is accomplished by the following
 steps.

7.2.1 Define the property

 A property is defined by completing the following template.
   To: ietf-calendar@imc.org
   Subject: Registration of text/calendar MIME property XXX
   Property name:
   Property purpose:
   Property value type(s):
   Property parameter (s):
   Conformance:
   Description:
   Format definition:
   Examples:
 The meaning of each field in the template is as follows.
 Property name: The name of the property, as it will appear in the
 body of an text/calendar MIME Content-Type "property: value" line to
 the left of the colon ":".
 Property purpose: The purpose of the property (e.g., to indicate a
 delegate for the event or to-do, etc.). Give a short but clear
 description.
 Property value type (s): Any of the valid value types for the
 property value needs to be specified. The default value type also
 needs to be specified. If a new value type is specified, it needs to
 be declared in this section.
 Property parameter (s): Any of the valid property parameters for the
 property needs to be specified.
 Conformance: The calendar components that the property can appear in
 needs to be specified.

Dawson & Stenerson Standards Track [Page 142] RFC 2445 iCalendar November 1998

 Description: Any special notes about the property, how it is to be
 used, etc.
 Format definition: The ABNF for the property definition needs to be
 specified.
 Examples: One or more examples of instances of the property needs to
 be specified.

7.2.2 Post the Property definition

 The property description MUST be posted to the new property
 discussion list, ietf-calendar@imc.org.

7.2.3 Allow a comment period

 Discussion on the new property MUST be allowed to take place on the
 list for a minimum of two weeks. Consensus MUST be reached on the
 property before proceeding to the next step.

7.2.4 Submit the property for approval

 Once the two-week comment period has elapsed, and the proposer is
 convinced consensus has been reached on the property, the
 registration application should be submitted to the Method Reviewer
 for approval. The Method Reviewer is appointed to the Application
 Area Directors and can either accept or reject the property
 registration. An accepted registration should be passed on by the
 Method Reviewer to the IANA for inclusion in the official IANA method
 registry. The registration can be rejected for any of the following
 reasons. 1) Insufficient comment period; 2) Consensus not reached; 3)
 Technical deficiencies raised on the list or elsewhere have not been
 addressed. The Method Reviewer's decision to reject a property can be
 appealed by the proposer to the IESG, or the objections raised can be
 addressed by the proposer and the property resubmitted.

7.3 Property Change Control

 Existing properties can be changed using the same process by which
 they were registered.
      1.           Define the change
      2.           Post the change
      3.           Allow a comment period
      4.           Submit the property for approval

Dawson & Stenerson Standards Track [Page 143] RFC 2445 iCalendar November 1998

 Note that the original author or any other interested party can
 propose a change to an existing property, but that such changes
 should only be proposed when there are serious omissions or errors in
 the published memo. The Method Reviewer can object to a change if it
 is not backward compatible, but is not required to do so.
 Property definitions can never be deleted from the IANA registry, but
 properties which are no longer believed to be useful can be declared
 OBSOLETE by a change to their "intended use" field.

8 References

 [IMIP]     Dawson, F., Mansour, S. and S. Silverberg, "iCalendar
            Message-based Interoperability Protocol (IMIP)", RFC 2447,
            November 1998.
 [ITIP]     Silverberg, S., Mansour, S., Dawson, F. and R. Hopson,
            "iCalendar Transport-Independent Interoperability Protocol
            (iTIP) : Scheduling Events, Busy Time, To-dos and Journal
            Entries", RFC 2446, November 1998.
 [ISO 8601] ISO 8601, "Data elements and interchange formats-
            Information interchange--Representation of dates and
            times", International Organization for Standardization,
            June, 1988.
 [ISO 9070] ISO/IEC 9070, "Information Technology_SGML Support
            Facilities--Registration Procedures for Public Text Owner
            Identifiers", Second Edition, International Organization
            for Standardization, April 1991.
 [RFC 822]  Crocker, D., "Standard for the Format of ARPA Internet
            Text Messages", STD 11, RFC 822, August 1982.
 [RFC 1738] Berners-Lee, T., Masinter, L. and M. McCahill, "Uniform
            Resource Locators (URL)", RFC 1738, December 1994.
 [RFC 1766] Alvestrand, H., "Tags for the Identification of
            Languages", RFC 1766, March 1995.
 [RFC 2045] Freed, N. and N. Borenstein, " Multipurpose Internet Mail
            Extensions (MIME) - Part One: Format of Internet Message
            Bodies", RFC 2045, November 1996.
 [RFC 2046] Freed, N. and N. Borenstein, " Multipurpose Internet Mail
            Extensions (MIME) - Part Two: Media Types", RFC 2046,
            November 1996.

Dawson & Stenerson Standards Track [Page 144] RFC 2445 iCalendar November 1998

 [RFC 2048] Freed, N., Klensin, J. and J. Postel, "Multipurpose
            Internet Mail Extensions (MIME) - Part Four: Registration
            Procedures", RFC 2048, January 1997.
 [RFC 2119] Bradner, S., "Key words for use in RFCs to Indicate
            Requirement Levels", BCP 14, RFC 2119, March 1997.
 [RFC 2234] Crocker, D. and P. Overell, "Augmented BNF for Syntax
            Specifications: ABNF", RFC 2234, November 1997.
 [RFC 2279] Yergeau, F., "UTF-8, a transformation format of ISO
            10646", RFC 2279, January 1998.
 [RFC 2425] Howes, T., Smith, M. and F. Dawson, "A MIME Content-Type
            for Directory Information", RFC 2425, September 1998.
 [RFC 2426] Dawson, F. and T. Howes, "vCard MIME Directory Profile",
            RFC 2426, September 1998.
 [TZ]       Olson, A.D., et al, Time zone code and data,
            ftp://elsie.nci.nih.gov/pub/, updated periodically.
 [VCAL]     Internet Mail Consortium, "vCalendar - The Electronic
            Calendaring and Scheduling Exchange Format",
            http://www.imc.org/pdi/vcal-10.txt, September 18, 1996.

9 Acknowledgments

 A hearty thanks to the IETF Calendaring and Scheduling Working Group
 and also the following individuals who have participated in the
 drafting, review and discussion of this memo:
 Roland Alden, Harald T. Alvestrand, Eric Berman, Denis Bigorgne, John
 Binici, Bill Bliss, Philippe Boucher, Steve Carter, Andre
 Courtemanche, Dave Crocker, David Curley, Alec Dun, John Evans, Ross
 Finlayson, Randell Flint, Ned Freed, Patrik Faltstrom, Chuck
 Grandgent, Mark Handley, Steve Hanna, Paul B. Hill, Paul Hoffman,
 Ross Hopson, Mark Horton, Daryl Huff, Bruce Kahn, C. Harald Koch,
 Ryan Jansen, Don Lavange, Antoine Leca, Theodore Lorek, Steve
 Mansour, Skip Montanaro, Keith Moore, Cecil Murray, Chris Newman,
 John Noerenberg, Ralph Patterson, Pete Resnick, Keith Rhodes, Robert
 Ripberger, John Rose, Doug Royer, Andras Salamar, Ted Schuh, Vinod
 Seraphin, Derrick Shadel, Ken Shan, Andrew Shuman, Steve Silverberg,
 William P. Spencer, John Sun, Mark Towfiq, Yvonne Tso, Robert Visnov,
 James L. Weiner, Mike Weston, William Wyatt.

Dawson & Stenerson Standards Track [Page 145] RFC 2445 iCalendar November 1998

10 Authors' and Chairs' Addresses

 The following address information is provided in a MIME-VCARD,
 Electronic Business Card, format.
 The authors of this memo are:
 BEGIN:VCARD
 VERSION:3.0
 N:Dawson;Frank
 FN:Frank Dawson
 ORG:Lotus Development Corporation
 ADR;TYPE=WORK,POSTAL,PARCEL:;;6544 Battleford Drive;
  Raleigh;NC;27613-3502;USA
 TEL;TYPE=WORK,MSG:+1-919-676-9515
 TEL;TYPE=WORK,FAX:+1-919-676-9564
 EMAIL;TYPE=PREF,INTERNET:Frank_Dawson@Lotus.com
 EMAIL;TYPE=INTERNET:fdawson@earthlink.net
 URL:http://home.earthlink.net/~fdawson
 END:VCARD
 BEGIN:VCARD
 VERSION:3.0
 N:Stenerson;Derik
 FN:Derik Stenerson
 ORG:Microsoft Corporation
 ADR;TYPE=WORK,POSTAL,PARCEL:;;One Microsoft Way;
  Redmond;WA;98052-6399;USA
 TEL;TYPE=WORK,MSG:+1-425-936-5522
 TEL;TYPE=WORK,FAX:+1-425-936-7329
 EMAIL;TYPE=INTERNET:deriks@Microsoft.com
 END:VCARD
 The iCalendar object is a result of the work of the Internet
 Engineering Task Force Calendaring and Scheduling Working Group. The
 chairmen of that working group are:
 BEGIN:VCARD
 VERSION:3.0
 N:Ganguly;Anik
 FN:Anik Ganguly
 ORG: Open Text Inc.
 ADR;TYPE=WORK,POSTAL,PARCEL:;Suite 101;38777 West Six Mile Road;
  Livonia;MI;48152;USA
 TEL;TYPE=WORK,MSG:+1-734-542-5955
 EMAIL;TYPE=INTERNET:ganguly@acm.org
 END:VCARD

Dawson & Stenerson Standards Track [Page 146] RFC 2445 iCalendar November 1998

 The co-chairman of that working group is:
 BEGIN:VCARD
 VERSION:3.0
 N:Moskowitz;Robert
 FN:Robert Moskowitz
 EMAIL;TYPE=INTERNET:rgm-ietf@htt-consult.com
 END:VCARD

Dawson & Stenerson Standards Track [Page 147] RFC 2445 iCalendar November 1998

11. Full Copyright Statement

 Copyright (C) The Internet Society (1998).  All Rights Reserved.
 This document and translations of it may be copied and furnished to
 others, and derivative works that comment on or otherwise explain it
 or assist in its implementation may be prepared, copied, published
 and distributed, in whole or in part, without restriction of any
 kind, provided that the above copyright notice and this paragraph are
 included on all such copies and derivative works.  However, this
 document itself may not be modified in any way, such as by removing
 the copyright notice or references to the Internet Society or other
 Internet organizations, except as needed for the purpose of
 developing Internet standards in which case the procedures for
 copyrights defined in the Internet Standards process must be
 followed, or as required to translate it into languages other than
 English.
 The limited permissions granted above are perpetual and will not be
 revoked by the Internet Society or its successors or assigns.
 This document and the information contained herein is provided on an
 "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
 TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
 BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
 HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
 MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.

Dawson & Stenerson Standards Track [Page 148]

/data/webs/external/dokuwiki/data/pages/rfc/rfc2445.txt · Last modified: 1998/11/13 17:12 by 127.0.0.1

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