Today an international group of scientists, diplomats, and timekeepers voted to end the leap second, which has been keeping Coordinated Universal Time (UTC) aligned with the time according to Earth’s rotation (UT1) within one second of difference.
A new system, called the “leap hour,” will allow the Earth’s rotation and official time to fall out of alignment by a full hour
https://gist.github.com/timvisee/fcda9bbdff88d45cc9061606b4b923ca
If your software is choking on completely expectable events, it it not sufficiently robust.
As you just proved, while it might be possible to write robust software that deals with dates/times, I wouldn’t bet on it, and it’s Definitely not practical to try.
But you are right that leap seconds were common enough to try and handle. There’s a bunch of ways to handle them though, each incompatible with the others.