Paul Evans

NAME

Time::timegm - a UTC version of mktime()

SYNOPSIS

 use Time::timegm qw( timegm );

 my $epoch = timegm( 0, 0, 0, 14, 6-1, 2012-1900 );

 print "2012-06-14 00:00:00 UTC happened at ",
    scalar localtime($epoch), " localtime\n";

DESCRIPTION

The POSIX standard provides three functions for converting between integer epoch values and 6-component "broken-down" time representations. localtime and gmtime convert an epoch into the 6 components of seconds, minutes, hours, day of month, month and year, in either local timezone or UTC. The mktime function converts a local broken-down time into an epoch value. However, POSIX does not provide a UTC version of this.

This module provides a function timegm which has this ability.

Unlike some other CPAN implementations of this behaviour, this version does not re-implement the time handling logic internally. It reuses the mktime and gmtime functions provided by the system to ensure its results are always consistent with the other functions.

FUNCTIONS

$epoch = timegm( $sec, $min, $hour, $mday, $mon, $year )

Returns the epoch integer value representing the time given by the 6 broken-down components.

As with POSIX::mktime it is not required that these values be within their "valid" ranges. This function will normalise values out of range. For example, the 25th hour of a day is normalised to the 1st hour of the following day; or the 0th month is normalised to the 12th month of the preceeding year.

COMPARISON WITH Time::Local

The Time::Local module also provides a function called timegm() with similar behaviour to this one. The differences are:

  • Time::timegm::timegm() handles denormalised values (that is, seconds or minutes outside of the range 0 to 59, hours outside 0 to 23, etc..) by adjusting the next largest unit (such that 61 seconds is 1 second of the next minute, etc). Time::Local::timegm() croaks on out-of-range input. Time::Local also provides a function timegm_nocheck() which does not croak but it is documented that the behavior is unspecified on out-of-range values.

  • Time::timegm::timegm() is implemented by a light XS wrapper around the timegm(3) or _mkgmtime(3) function provided by the platform's C library if such a function is provided, so its behaviour is consistent with the rest of the platform. Time::Local re-implements the logic in perl code. Time::timegm will fall back to a perl implementation only if the XS one cannot be used.

AUTHOR

Paul Evans <leonerd@leonerd.org.uk>




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