So now, rather than remembering what timezone someone/some location is, you have to remember instead what is "normal daytime" for that locale. Everyone worldwide isn't going to operate on the same schedule regardless on the position of the sun.
We have these devices called computers which are quite excellent at this kind of task.
Snark aside, it wouldn't be that hard to have the clocks all set to UTC, and then a second "day equivalent" clock that's used only for translation, but not for actual timekeeping.
