[ythn]

The simple thing to do then is to call an `isLeapYear` function that abstracts any complexity.

Abstraction allows you to hide complexity and make it a simple, reusable part again.

[DannyB2]

But I could write a simpler (incorrect) leap year function than yours!

[ythn]

You missed the point of the article if you interpreted it as correctness being intentionally sacrificed for simplicity.

Plus, a complete leap year implementation is already what I would consider simple and most standard libraries already have an implementation for it you can use directly.