timegm(3) — Linux manual page

NAME | LIBRARY | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | ATTRIBUTES | STANDARDS | HISTORY | SEE ALSO | COLOPHON

timegm(3)               Library Functions Manual               timegm(3)

NAME         top

       timegm, timelocal - inverses of gmtime and localtime

LIBRARY         top

       Standard C library (libc, -lc)

SYNOPSIS         top

       #include <time.h>

       [[deprecated]] 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         top

       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         top

       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
       error.

ERRORS         top

       EOVERFLOW
              The result cannot be represented.

ATTRIBUTES         top

       For an explanation of the terms used in this section, see
       attributes(7).
       ┌──────────────────────────┬───────────────┬────────────────────┐
       │ Interface                Attribute     Value              │
       ├──────────────────────────┼───────────────┼────────────────────┤
       │ timelocal(), timegm()    │ Thread safety │ MT-Safe env locale │
       └──────────────────────────┴───────────────┴────────────────────┘

STANDARDS         top

       BSD.

HISTORY         top

       GNU, BSD.

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

SEE ALSO         top

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

COLOPHON         top

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Linux man-pages 6.9.1          2024-05-02                      timegm(3)

Pages that refer to this page: ctime(3)