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);

[download]

One second thought, the following seems better, especially if the initial list of times is already sorted. 

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;
   }
}

[download]

In reply to Re: epoch reduction by ikegami
in thread epoch reduction by neilwatson

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