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TIMEGM(3) Linux Programmer's Manual TIMEGM(3)

NAME

     timegm, timelocal - inverses of gmtime and localtime

SYNOPSIS

     #include <time.h>

     time_t timelocal(struct tm *tm);

     time_t timegm(struct tm *tm);

 Feature Test Macro Requirements for glibc (see feature_test_macros(7)):

     timelocal(), timegm():
         Since glibc 2.19:
             _DEFAULT_SOURCE
         Glibc 2.19 and earlier:
             _BSD_SOURCE || _SVID_SOURCE

DESCRIPTION

     The functions timelocal() and timegm() are the inverses of localtime(3)
     and gmtime(3).  Both functions take a broken-down time and  convert  it
     to  calendar  time (seconds since the Epoch, 1970-01-01 00:00:00 +0000,
     UTC).  The difference between the two  functions  is  that  timelocal()
     takes  the local timezone into account when doing the conversion, while
     timegm() takes the input value to be Coordinated Universal Time  (UTC).

RETURN VALUE

     On success, these functions return the calendar time (seconds since the
     Epoch), expressed as a value of type time_t.  On error, they return the
     value (time_t) -1 and set errno to indicate the cause of the error.

ERRORS

     EOVERFLOW
            The result cannot be represented.

ATTRIBUTES

     For   an   explanation   of   the  terms  used  in  this  section,  see
     attributes(7).

     allbox; lbw21 lb lb l l l.  Interface Attribute Value  T{  timelocal(),
     timegm() T}   Thread safety  MT-Safe env locale

CONFORMING TO

     These functions are nonstandard GNU extensions that are also present on
     the BSDs.  Avoid their use.

NOTES

     The timelocal() function is equivalent to the POSIX  standard  function
     mktime(3).  There is no reason to ever use it.