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(): _BSD_SOURCE || _SVID_SOURCE

DESCRIPTION

       The functions timelocal() and timegm() are the inverses of localtime(3) and gmtime(3).

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; see NOTES.

NOTES

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

       For a portable version of timegm(), set the TZ environment variable to UTC, call mktime(3)
       and restore the value of TZ.  Something like

           #include <time.h>
           #include <stdlib.h>

           time_t
           my_timegm(struct tm *tm)
           {
               time_t ret;
               char *tz;

               tz = getenv("TZ");
               if (tz)
                   tz = strdup(tz);
               setenv("TZ", "", 1);
               tzset();
               ret = mktime(tm);
               if (tz) {
                   setenv("TZ", tz, 1);
                   free(tz);
               } else
                   unsetenv("TZ");
               tzset();
               return ret;
           }

SEE ALSO

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

COLOPHON

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       project,  information  about  reporting  bugs, and the latest version of this page, can be
       found at http://www.kernel.org/doc/man-pages/.