We assume people who can figure out the exact day of the week for any date you throw at them are geniuses or some sort of clairvoyant, but the bubble bursting truth is they're just doing a type of mental magic trick.
More specifically they're using an algorithm developed by mathematician John H. Conway in 1973 called the Doomsday rule, and as you'll see in this video by It's Ok To Be Smart using this algorithm isn't as hard as you think.
Now with a little practice you can start wowing people with your astounding mental abilities!
-Via Geeks Are Sexy