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);