use DateTime;
use DateTime::TimeZone;

my $dt = DateTime->new(
      year       => 2013,
      month      => 4,
      day        => 15,
      hour       => 12,
      minute     => 45,
      second     => 47,
      time_zone  => 'Europe/Berlin',
  );

my $tz = DateTime::TimeZone->new( name => 'US/Pacific' );

my $offset = $tz->offset_for_datetime($dt);

print qq($offset\n);

print DateTime::TimeZone->offset_as_string( $offset ) . qq(\n);

print qq($dt->hour\n); 

$dt->set_time_zone( 'US/Pacific' );

print qq($dt->hour\n);