I have a friend who, if I tell him my birth date, can tell me what day of the week I was born on, but he won't tell me how it is done.
Can you?
Thank you.

Is he doing it in real time, not looking at the calendar? :)

Yes. In real time, and it doesn't take him very long.

Go to the following link and read about the king of memory, Tony Buzan
http://members.optusnet.com.au/~charles57/Creative/Authors/ABuzan.htm

If you got knocked on the head you could remember those things too. Saw it on a TV show.

Thanks for that, but I think there must be a formula behind it somewhere.

This website provides such a formula:

http://mathforum.org/library/drmath/view/56757.html

Thanks for that reinsuranc.