use Time::Local qw( timelocal );

$ENV{TZ} = 'America/St_Johns';

for my $time (
   timelocal(0, 25, 16, 26, 4-1, 2007),  # 16th hour of 2007-04-26
   timelocal(0, 35, 16, 26, 4-1, 2007),  # 16th hour of 2007-04-26
) {
   my $hour = int( $time / 3600 ) * 3600;
   print(scalar(localtime($time)), "\n");

   # Should print the same value for both, but doesn't.
   print("$hour\n");
}