Arguably it's worse if 00:33 on 2024.12.26 has to get run through another function to get the true value of 2024.12.25 T 23:59.

The problem is leap seconds. Software just wasn't designed to handle 86401 seconds in a day, and caused incidents at Google, Cloudflare, Quantus, and others. Worried that resolving all possible bugs related to days with 86401 seconds in them was going to be impossible to get right, Google decided to smear that leap second so that the last "second" isn't.

And if you've not seen it, there's the falsehoods programmers believe about time article.