README
1NAME
2 `Time::timegm' - a UTC version of `mktime()'
3
4SYNOPSIS
5 use Time::timegm qw( timegm );
6
7 my $epoch = timegm( 0, 0, 0, 14, 6-1, 2012-1900 );
8
9 print "2012-06-14 00:00:00 UTC happened at ",
10 scalar localtime($epoch), " localtime\n";
11
12DESCRIPTION
13 The POSIX standard provides three functions for converting between
14 integer epoch values and 6-component "broken-down" time representations.
15 `localtime' and `gmtime' convert an epoch into the 6 components of
16 seconds, minutes, hours, day of month, month and year, in either local
17 timezone or UTC. The `mktime' function converts a local broken-down time
18 into an epoch value. However, `POSIX' does not provide a UTC version of
19 this.
20
21 This module provides a function `timegm' which has this ability.
22
23 Unlike some other CPAN implementations of this behaviour, this version
24 does not re-implement the time handling logic internally. It reuses the
25 `mktime' and `gmtime' functions provided by the system to ensure its
26 results are always consistent with the other functions.
27
28FUNCTIONS
29 $epoch = timegm( $sec, $min, $hour, $mday, $mon, $year )
30 Returns the epoch integer value representing the time given by the 6
31 broken-down components.
32
33 As with `POSIX::mktime' it is *not* required that these values be within
34 their "valid" ranges. This function will normalise values out of range.
35 For example, the 25th hour of a day is normalised to the 1st hour of the
36 following day; or the 0th month is normalised to the 12th month of the
37 preceeding year.
38
39COMPARISON WITH Time::Local
40 The Time::Local module also provides a function called `timegm()' with
41 similar behaviour to this one. The differences are:
42
43 * `Time::timegm::timegm()' handles denormalised values (that is, seconds
44 or minutes outside of the range 0 to 59, hours outside 0 to 23, etc..)
45 by adjusting the next largest unit (such that 61 seconds is 1 second
46 of the next minute, etc). `Time::Local::timegm()' croaks on
47 out-of-range input. `Time::Local' also provides a function
48 `timegm_nocheck()' which does not croak but it is documented that the
49 behavior is unspecified on out-of-range values.
50
51 * `Time::timegm::timegm()' is implemented by a light XS wrapper around
52 the `timegm(3)' or `_mkgmtime(3)' function provided by the platform's
53 C library if such a function is provided, so its behaviour is
54 consistent with the rest of the platform. `Time::Local' re-implements
55 the logic in perl code. `Time::timegm' will fall back to a perl
56 implementation only if the XS one cannot be used.
57
58AUTHOR
59 Paul Evans <leonerd@leonerd.org.uk>
60
61