Forget embedded systems, cisco routers seem not to handle time zones well. I ended up with a discussion about timezones with one of my network guys and he admitted it was much easier to set the system time on cisco devices to GMT then it was to make the daylight saving switch. They don't have complete timezone databases apparently.

The crux of my conversation with him is that it matters where you are just as much when you are. The fact that America is two weeks off from the rest of the world caused no end of annoyances these past two weeks. It also ended up with lots of debates about how "wall clock time" has little do with the actual time especially when talking about past or future.

(Think 4pm in London 5 moths from now, what time will that be in NY? What about Brazil? Is that the same time of the day if it's 6 months from now?)

Too many internal systems have an incomplete vision of what time means to them and it rarely holds up. I could go on, but I leave it with this. If you can help it, store points in time in a unix timestamp (or at least UTC) and avoid having to write scheduling software.