#!/usr/bin/perl

print "see http://stackoverflow.com/questions/8221841/how-to-compare-string-date-time-in-perl \n";


$date1 = "11:56:41, 11/22/2011";
$date2 = "11:20:41, 11/20/2011";

$date1c  = to_comparable($date1) ;
print "$date1  $date1c\n";
$date2c  = to_comparable($date2) ;
print "$date2  $date2c\n";
if (to_comparable($date2) > to_comparable($date1)) {
   print "YES\n";
} else {
   print "NO\n";
}

$date1 = "2011:10:25 11:56:41";
$date2 = "2011:12:25 11:06:41";
$date1c  = conv_datetime($date1) ;
print "$date1  $date1c\n";
$date2c  = conv_datetime($date2) ;
print "$date2  $date2c\n";


sub to_comparable {
   my ($date) = @_;
   my ($H,$M,$S,$d,$m,$Y) = $date =~ m{^([0-9]{2}):([0-9]{2}):([0-9]{2}), ([0-9]{2})/([0-9]{2})/([0-9]{4})\z}
      or die;
   return "$Y$m$d$H$M$S";
}

sub conv_datetime {
   my ($date) = @_;
   my ($Y,$m,$d,$H,$M,$S) = $date =~ m{^([0-9]{4}):([0-9]{2}):([0-9]{2}) ([0-9]{2}):([0-9]{2}):([0-9]{2})\z}
      or die;
   return "$Y$m$d$H$M$S";
}



============================================
$ perl date.pl
see http://stackoverflow.com/questions/8221841/how-to-compare-string-date-time-in-perl
11:56:41, 11/22/2011  20112211115641
11:20:41, 11/20/2011  20112011112041
NO
2011:10:25 11:56:41  20111025115641
2011:12:25 11:06:41  20111225110641