#!/usr/bin/perl

use strict;
use warnings;

use DateTime;

for my $year (1970..2020) {

  my $winter_dt = DateTime->new(
		       year   => $year,
		       month  => 1,
		       day    => 7,
		       hour   => 16,
		       minute => 12,
		       second => 47,
		       time_zone => 'Europe/London',
		      );

  print "winter $year: ", $winter_dt->time_zone->short_name_for_datetime($winter_dt), " (", $winter_dt->time_zone->offset_for_datetime($winter_dt), ") ... ";

  my $summer_dt = DateTime->new(
		       year   => $year,
		       month  => 6,
		       day    => 7,
		       hour   => 16,
		       minute => 12,
		       second => 47,
		       time_zone => 'Europe/London',
		      );

  print "summer $year: ", $summer_dt->time_zone->short_name_for_datetime($summer_dt), " (", $summer_dt->time_zone->offset_for_datetime($summer_dt), ")\n";

}