Day of the Week Calculator

How it works

The date is converted to a day count from a fixed reference date; the weekday is that count modulo 7. By hand, you can use Zeller’s congruence or the “Doomsday” method devised by John Conway, which relies on easy-to-remember dates (4/4, 6/6, 8/8, 10/10, 12/12) that always share a weekday within a year.

Worked example