This kind of thing becomes a lot of fun when you're trying to schedule a regular international call between e.g. the US and the UK, where the offset in hours changes four times per year because their daylight saving adjustments are not simultaneous.

When I say "becomes a lot of fun" what I actually mean is that this observation lets us understand very quickly that the problem is not generally solvable. One way or another, somebody's 9 o'clock meeting is going to suddenly take place at 10. Having accepted that, we can push through the idealism and start working actual solutions like the one you described - have the user attach the regularly scheduled meeting time specifically to the UK or to the US.