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>