The Method

What Day Was That?

Roll a date, or enter your own. Work it out in your head, then check yourself.

Add four numbers, apply one century adjustment, divide by seven, and read off the remainder.

“Leap year” means a real leap year. 1900 was not one — divisible by 100 but not 400 — so January and February 1900 use 1 and 4. 2000 was one.
The century adjustment here covers only the 1900s and 2000s, which is exactly the range this page rolls from.