use DateTime           qw( );
use DateTime::TimeZone qw( );

my $old_tz = DateTime::TimeZone->new( name => "+0100" );
my $new_tz = DateTime::TimeZone->new( name => "Europe/Rome" );

for my $date (
  [ 2020, 12, 2, 1, 0 ],
  [ 2021,  7, 2, 1, 0 ],
) {
   my $dt = DateTime->new(
      year =>   => $date->[0],
      month     => $date->[1],
      day       => $date->[2],
      hour      => $date->[3],
      minute    => $date->[4],
      time_zone => $old_tz,
   );

   say $dt->strftime("%FT%T%z");

   $dt->set_time_zone($new_tz);

   say $dt->strftime("%FT%T%z");
}