Today is called Doomsday... I don't really know why, but it's always the last day of February - not just the 29th. But I bring this to your attention because of this cool fact: Whatever day of the week it falls, Mon, Tue, Wed, Thr, Fri, Sat or Sun, it repeats on even numbers: 4 Apr (4/4), 6 Jun (6/6), 8 Aug (8/8), 10/10, 12/12. The odd numbers are linked 9/5 and 7/11 with their inverse too, 5/9 and 11/7 are Monday's this year. 7 Mar is always the same day as Doomsday. https://en.wikipedia.org/wiki/Doomsday_rule So now you can figure out any day of the year. For example, when is Christmas? 12/12 is Monday so add 14 days (2 weeks) and subtract one day (12+14=26): Christmas is on Sunday this year. Enjoy.