timegm(3) - Linux manual page (original) (raw)

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)](../man3/localtime.3.html) and [gmtime(3)](../man3/gmtime.3.html).  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 _timet_.  On error,
   they return the value _(timet) -1_ and set _[errno](../man3/errno.3.html)_ 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)](../man7/attributes.7.html).
   ┌───────────────────────────┬───────────────┬────────────────────┐
   │ **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)](../man3/mktime.3.html).  There is no reason to ever use it.

SEE ALSO top

   [gmtime(3)](../man3/gmtime.3.html), [localtime(3)](../man3/localtime.3.html), [mktime(3)](../man3/mktime.3.html), [tzset(3)](../man3/tzset.3.html)

COLOPHON top

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Linux man-pages 6.10 2024-07-23 timegm(3)

Pages that refer to this page:ctime(3)