use List::Util qw( max );
use POSIX      qw( strftime );

my %by_date;
for my $time (@times) {
   my $date = strftime('%Y-%m-%d', localtime($time));
   $by_date{$date} = max($by_date{$date}||0, $time);
}

my @filtered_times = map $by_date{$_}, sort keys(%by_date);

##</code><code>##

use POSIX qw( strftime );

my $last_date = '';
my @filtered_times;
for my $time (sort { $a <=> $b } @times) {
   my $date = strftime('%Y-%m-%d', localtime($time));
   if ($date eq $last_date) {
      $filtered_times[-1] = $time;
   } else {
      push @filtered_times, $time;
      $last_date = $date;
   }
}