How can some people tell the day of the week with just date?

Question

I have come across some people that if you tell them any date, they can do some calculation in their mind and tell you correctly what day of the week it was or will be.

For example, if you ask what day it was on January 30, 2002. They can tell you it was Wednesday. How do they do that? If any of you know, can you please tell me.

Much thanks in advance!

Answer 1

If you notice, as each year passes, the day of the week that each day of the month lands on is one day later, unless a February 29th fell between those two. With a little brain power, anyone can do this.

Given the day of the month that January 30, 2007 falls on (Tuesday), it was Monday last year, Sunday in 2005, Friday in 2004 (notice the leap day), Thursday in 2003, and Wednesday in 2002. :-)

Answer 2

A year is 52 weeks and one day long
if one year ends on Mon the next year will end on Tue ( same with dates June 1 - Mon then Tue ) calculate the leap years ( add one more day ) and you are done - so really you just need to memorize what the leap years are

Answer 3

With the help of calander