I once worked with smart meters for electricity consumption that do run 24/7. Leap seconds were not an issue but we had a very similar one now that I think about it: DST shenanigans!
Like how much time is there between 2 and 3 am? Usually one hour, but sometimes 2 and also sometimes 0. It looks simple at first but it creates a lot of edge cases that your business logic now needs to handle and we had a fairly complex system for this.
I can relate:
My son is born at 02h30 right DST change time.
It tooks 3 f*cking days to get his birth registered in the Hospital new birth registration system.
The hospital (at the time) just got digitalized and most systems where not able to agree if he was born after or before DST changes.
PS: I guess he is born fated to be a software QA later on.
This commenter says he has different birth dates in different countries' sytems, which is correct if you consider the exact time of birth, but... that's probably a bug? https://news.ycombinator.com/item?id=48853128