Ahh, it looks like I forgot that strtotime only works for english date strings, and I'm using the month name. This should fix it for you.
Line 177 of showday.inc.php has this:
$date_string = "{$ubbt_lang[$mname]} $day $year 12:01 PM";
Change that, to this:
$date_string = "$month/$day/$year 12:01 PM";
