What day is it?
There sometimes comes situations when you need to know the weekday of some particular date. If it's close enough to the current date, or some other date you know the weekday it's quite simple to count the weekday. But when you don't have any reference point it becomes a trickier.
The doomsday algorithm solves that problem. It's a simple mathematical formula you can use to calculate the weekday of any date. In addition to knowing the formula you also need to memorize few set of rules to assign certain numbers based on the century the date is on and a number for each month.