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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).

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

SEE ALSO

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

COLOPHON

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