User: thisisjoel

"Crunching" the numbers

On: This Rare Friday the 13th

If anyone else wants to "crunch" those numbers, here's some Perl:

use Date::Calc qw( Add_Delta_Days Day_of_Week );

my $MAX_YEAR=3000;
my @date = (1,1,1);

sub summer { $a = 0; foreach (@_) { $a += $_ } $a }

while( $date[0] < $MAX_YEAR ) {
@date = Add_Delta_Days( @date, 1 );
if( $date[2] == 13
&& Day_of_Week( @date ) == 5
&& summer( split '', sprintf( "%04d-%02d-%02d", @date ) ) == 13
) {
printf( "%04d-%02d-%02d\n", @date );
}
}

I get 2006-01-13 as the most recent occurrence.