Or maybe there’s just no consistent relationship between what a clock on the East and West coast of America say, and a call can’t be scheduled between them.
If you get rid of timezones they all say the same time, no? If you want to schedule a call you just say the time and save the timzone offset fiddling.
The real problem with time and date is that it has to fit social and natural systems as well as actual passage of time.
Can you give any more concrete examples? None come to mind beyond habit, which is not an immutable thing.