As the new year begins, so does my annual tradition of writing my review of 2025 and setting goals for 2026 1. Alongside the more serious ones, I wanted to pick up a few lighter skills too.
Recently, I’ve been reading about the Doomsday rule, an algorithm that allows you to determine the day of the week for any given date. With a bit of memorisation —2 the anchor day for each century, and one anchor date per month — you can efficiently calculate the day for any date!
To help myself learn this 3 more effectively, I built Day Guesser, a small web app to quiz myself. It’s not too complicated; built with simple HTML, CSS and JavaScript, with support for Markdown and LaTeX. Occasionally, web development ends up not making me contemplate the quickest way to end myself, and fortunately, this was one of those times!
Currently, I’m at about 15 seconds per mental computation and I’d like to improve that quite a bit. John Conway — yes, the creator of the game of Life John Conway — who devised the algorithm, could allegedly give the correct answer in under two seconds per query!