Try something like

use strict;
use warnings;

my @dates = ( 'Oct 16 2004 11:09:19:943AM',
              'Mar 3 2007 10:30:31:170PM',
            );

foreach my $date (@dates) {
    my ($month, $day, $year, $time) = split( /\s+/, $date );
    my $sorting_date 
        = $year . $date_hash{$month} . sprintf( '%02d', $day);
}
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