We use modular arithmetic all the time ... It's called Zeller's formula and here it is: Let's do some examples. I'll pick a date we know: December 7, 1941 was a Sunday. The corresponding numbers ...

You may never have heard of modular arithmetic, but you use it every day without the slightest difficulty. In this system, numbers wrap around when they reach a certain size called the modulus ...

I now know that this is actually a part of math called modular arithmetic. Sometimes it’s informally called clock arithmetic, because it’s like how we tell the time: When we get around to 12 ...