Dr. Conway developed a sweet method (called the Doomsday Algorithm) to determine the day of the week for any day in history. It takes some practice, but dealing with the current year is pretty simple, provided you know the Doomsday.
Doomsday 2013 is Friday*.
- This means that the following dates are all Thursdays: 4/4, 6/6, 8/8, 10/10, 12/12.
- If you work nine to five at the local 7-11, you can remember four more Thursdays: 9/5, 7/11, 5/9, 11/7.
- Einstein’s birthday = Pi Day = 3/14 = Thursday.
- The last day of February (2/29 this year) is a Thursday.
- Lastly, 1/3 is Thursday (3 out of 4 years it’s the 3rd… but on leap years it’s the 4th).
Adding days of the week is easier when you treat them as numbers: mONEday, TWOsday, 3ednesday, FOURsday, 5day, S6turday (Treat Sunday as 0 - "nunday"). What's ten days past Wednesday? 10 + 3 = 13. Take out any multiples of 7 and you have 6 (Saturday).
*In case you’re interested, the link up top does a thorough job of teaching the method, but here’s the quick version. Start with the century day. For 2000 it is Tuesday (2). Then look at the 2-digit year, 14, and ask how many 12’s are in it. (1). What is the remainder? (2) How many 4’s are in this number? (0). Add up (2)+(1)+(2)+(0) = 5 = 5th day of the week = Friday.
Craziness? How about one more example from the future: 2055. Century day is still (2). How many 12’s in 55? (4). What is the remainder? (7). How many 4’s in this number? (1). Add ‘em up: (2)+(4)+(7)+(1) = 14. Take out multiples of 7 and you get 0. The 0th day of the week is Sunday. Now you can find the day of the week for any date in 2055.