This is a calculator that can tell you the day of the week for any date after 1900. Controls: For month and day, click the arrows to increase or decrease. For year, hover over a digit, and press a number key. The digit will change to that number. Press 'h' to see how it's done, press 'c' to close.
I learned this technique not long ago, and I wanted to make it a Scratch project. If you want to know WHY it works, just ask me, @Sporcler ;D