A leap year check in three instructions

If you need to know a leap year and it's before the year 6000, I made an interactive calculator and visualization [1].

It's >3 machine instructions (and I admire the mathematical tricks included in the post), but it does do thousands of calculations fairly quickly :)

[1] https://calculang.dev/examples-viewer?id=leap-year

Please make stuff fit into viewport width, hard to use on mobile as it stands :)

Thanks for the prompt! I made a new gallery that's mobile friendly and I almost forgot why I need to land it - adding it to the list!