Re: I don't see what the fuss is about
Hopefully no one rolls their own time functions these days. The problem is when you use the time. You might find things happening twice, or two events having the same timestamp or causality appearing to be broken (if time went backwards briefly). Depending on your system this might be "super bad".
I think the crux of it is you tend to assume time goes inexorably forward. It doesn't do that with a positive leap second (if you convert out of UTC).