Changing the timezone is as easy as ->set_time_zone()

Example TZ conversion in Perl

#!/usr/bin/perl -w
use 5.010;
use strict;
use warnings;
use autodie;
use DateTime;

my $dt = DateTime->now;

foreach my $timezone ( qw( Australia/Sydney GMT America/Los_Angeles ) ) {

    $dt->set_time_zone( $timezone );;

    printf(
        "%20s    %10s %3s %2s:%2s\n",
        $timezone, $dt->ymd, $dt->day_abbr, $dt->hour, $dt->minute
    );

}

__END__

    Australia/Sydney    2009-07-31 Fri 13:11
                 GMT    2009-07-31 Fri  3:11
 America/Los_Angeles    2009-07-30 Thu 20:11