Section (3) timegm
timegm, timelocal — inverses of gmtime and localtime
||struct tm *tm
||struct tm *tm
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).
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
−1 and set
errno to indicate the cause of the
For an explanation of the terms used in this section, see attributes(7).
||Thread safety||MT-Safe env locale|
These functions are nonstandard GNU extensions that are also present on the BSDs. Avoid their use.
timelocal() function is
equivalent to the POSIX standard function mktime(3). There is no
reason to ever use it.
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