#!usr/bin/perl
use say;
use strict;
use warnings;
use DateTime;
use DateTime::TimeZone;

sub TimeZone {
    my ($dt) = @_;
    my $tz = $dt->time_zone();
    my $offset = $tz->offset_for_datetime($dt);
    return $offset;
}

my $dt = DateTime->new(
    year       => 1964,
    month      => 10,
    day        => 16,
    hour       => 16,
    minute     => 12,
    second     => 47,
    nanosecond => 500000000,
    time_zone  => 'Asia/Taipei',
    );

my $tz = DateTime::TimeZone->new( name => 'America/Chicago' );
my $offset = $tz->offset_for_datetime($dt);

say TimeZone($dt);
say $offset;

__END__

$ perl test.pl
28800
-18000