We usually do one-week cycles, with something like five-day Days and two-day Nights, so there’s plenty of time in there for a player in any timezone. While it’s theoretically possible to get literal last-minute vote shenanigans or the like, and thus it’s theoretically nice to be online at that time, in practice, it very seldom comes up.
EDIT:
Oh, and games typically last about eight weeks or so, but most people will be out of it by then, and of those who are left it’s usually not very time-demanding.