in reply to
"Should be a simple thing" not going well for me
I prefer DateTime::Format::DateManip over the module you have selected. This provides an object with all the exposed methods allowed for DateTime while still providing some parsing of date strings.
#! C:/Perl/bin/perl
use Modern::Perl;
use DateTime::Format::DateManip;
my $dt = DateTime::Format::DateManip->parse_datetime(
"2011-07-24T17:46:33Z"
);
say $dt;
# Lock down the parsed time zone
$dt->set_time_zone( 'UTC' );
say $dt;
# change the time zone
$dt->set_time_zone( "America/North_Dakota/Center" );
say $dt;
Output
# 2011-07-24T17:46:33
# 2011-07-24T17:46:33
# 2011-07-24T12:46:33