Unfortunately, it's still broken. It doesn't account for timezones whose difference from UTC is not a multiple of 60 minutes. For example, you code doesn't work in Newfoundland.

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");
}
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Thu Apr 26 16:25:00 2007
1177610400
Thu Apr 26 16:35:00 2007
1177614000
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