timegm

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).

       +----------------------+---------------+--------------------+
       |Interface             | Attribute     | Value              |
       +----------------------+---------------+--------------------+
       |timelocal(), timegm() | 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.

SEE ALSO
       gmtime(3), localtime(3), mktime(3), tzset(3)

COLOPHON
       This  page  is  part of release 4.15 of the Linux man-pages project.  A
       description of the project, information about reporting bugs,  and  the
       latest     version     of     this    page,    can    be    found    at
       https://www.kernel.org/doc/man-pages/.

GNU                               2016-12-12                         TIMEGM(3)
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