One of my fellow contributors here recently wrote a post about leap years and why we have them. This reminded me of modular arithmetic and the formula for calculating the day of the week for any date ...

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; it is ...

The Monthly publishes articles, as well as notes and other features, about mathematics and the profession. Its readers span a broad spectrum of mathematical interests, and include professional ...