How to calculate the day of the week for a given date (idea)

For posterity, here's how to get the Doomsday for any century:

Memorize this: Sun-Tue-Wed-Fri. Century Doomsdays all fall on one of these days. (Mnemonic: your _son_ is going _to_ get married this Friday.)

Now remember that 1900 = Wednesday (Conway says "We-in-dis-day" -- a rather dated mnemonic as of this writeup, but maybe your birthday was in the 1900s).

The last thing to remember is that the '00' years always follow "Sun-Tue-Wed-Fri" in reverse order. So if 1900 = Wednesday, 2000 = Tuesday. You can sorta visualize this:

      S T W F
1600    *
1700  *
1800        *
1900      *
2000    *
2100  *
2200        *
2300      *