.\" Copyright (C) 2001 Andries Brouwer <aeb@cwi.nl>

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.TH TIMEGM 3 2016-12-12 "GNU" "Linux Programmer's Manual"

.SH NAME

timegm, timelocal \- inverses of gmtime and localtime

.SH SYNOPSIS

.nf

.B #include <time.h>

.PP

.BI "time_t timelocal(struct tm *" tm );

.PP

.BI "time_t timegm(struct tm *" tm );

.PP

.fi

.in -4n

Feature Test Macro Requirements for glibc (see

.BR feature_test_macros (7)):

.in

.PP

.BR timelocal (),

.BR timegm ():

    Since glibc 2.19:

        _DEFAULT_SOURCE

    Glibc 2.19 and earlier:

        _BSD_SOURCE || _SVID_SOURCE

.SH DESCRIPTION

The functions

.BR timelocal ()

and

.BR timegm ()

are the inverses of

.BR localtime (3)

and

.BR 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

.BR timelocal ()

takes the local timezone into account when doing the conversion, while

.BR timegm ()

takes the input value to be Coordinated Universal Time (UTC).

.SH RETURN VALUE

On success,

these functions return the calendar time (seconds since the Epoch),

expressed as a value of type

.IR time_t .

On error, they return the value

.IR "(time_t)\ -1"

and set

.I errno

to indicate the cause of the error.

.SH ERRORS

.TP

.B EOVERFLOW

The result cannot be represented.

.SH ATTRIBUTES

For an explanation of the terms used in this section, see

.BR attributes (7).

.TS

allbox;

lbw21 lb lb

l l l.

Interface	Attribute	Value

T{

.BR timelocal (),

.BR timegm ()

T}	Thread safety	MT-Safe env locale

.TE

.SH CONFORMING TO

These functions are nonstandard GNU extensions

that are also present on the BSDs.

Avoid their use.

.SH NOTES

The

.BR timelocal ()

function is equivalent to the POSIX standard function

.BR mktime (3).

There is no reason to ever use it.

.SH SEE ALSO

.BR gmtime (3),

.BR localtime (3),

.BR mktime (3),

.BR tzset (3)

.SH COLOPHON

This page is part of release 4.15 of the Linux

.I 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/.