Your main requirement seems to simply be to "determine what day it was," and you can do that with several CPAN modules. I really like Time::Piece

use strict;
use warnings;
use Time::Piece;

my $date = shift || '1999-12-31';
my $time = Time::Piece->strptime( $date, '%Y-%m-%d' );
print $time, $/;
print $time->fullday, $/;
[download]

L-LL-L--L-LL-L--L-LL-L--
-R--R-RR-R--R-RR-R--R-RR
B--B--B--B--B--B--B--B--
H---H---H---H---H---H---
(the triplet paradiddle with high-hat)