Ok. Here's the Golf. Given a 4-digit year from 1 through whenever, return 0-6 where 0 is sunday and 6 is saturday, for the day of Christmas.

I've got it at a cool 67. :-) 

my @days = qw(Sunday Monday Tuesday Wednesday Thursday Friday Saturday
+);

my $day = f($ARGV[0] || 2001);
print $days[$day], $/;

sub f {
#234567890#234567890#234567890#234567890#234567890#234567890#234567890
+#234567890
$b=1;for(1..pop){$b++;$b++if!$_%4;$b--if!$_%100;$b++if!$_%400}$b%=7
}

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In reply to Golfing the day of Christmas by dragonchild
in thread Christmas Coding Blues by cacharbe

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