Alt text:
It's not just time zones and leap seconds. SI seconds on Earth are slower because of relativity, so there are time standards for space stuff (TCB, TGC) that use faster SI seconds than UTC/Unix time. T2 - T1 = [God doesn't know and the Devil isn't telling.]
It's easier to understand, easier to review for correctness, and less likely to cause problems with additional changes in the future. Even though it sounds counterintuitive, software developers generally try to write as little code as possible. Any code you write is a potential liability that has to be maintained, so if you can instead just call code that others have already written and that has been tested, you'll want to do that. (Note that "less code" doesn't mean fewer lines of code, it means less logical complexity, which is often, but not always, also less in terms of characters/lines)
So like my english teacher taught me. Keep It Stupid Simple(though he would say keep it simple stupid to some people in class i am just realizing now 20+ years later)
Exactly that! KISS is an often cited rule among software devs.