Except even locally time is different for different people. People work nights, mornings, afternoons. Some shops open at 6am, others at 9am. Some people get up at 5, others and noon.
You still learn that x time is your time to do y, and people will quickly adapt to whatever number x happens to have.
We only associate 9am with anything because we learned to. We could just as easily learn a different number, and people with different work schedules do just that.
> Except even locally time is different for different people.
If you say "9pm local time", everyone knows it's the evening no matter if it's the time you go to bed or stand up because you work the night shift.
If a book says someone slept until 1pm you now they slept until mid day, no mater where the story plays. You don't have to go to the internet and look up if where he lives 1pm is morning, evening, night, etc.