That has been established for a long time. GMT is the reference time. Time zones are designed to allow us to keep our circadian rhythm in sync with the clocks. E.g. lunchtime and midday are at 1200. Otherwise Californians will be having lunch at 0500, while India would have it at 1730. That would get very confusing for travellers, very quickly.
It was extended further with Unix timestamps. They just count up seconds. No faffing with dates and conversions, no leap seconds or time zone changes to track. Just pure, unadulterated time. Unfortunately people get weird, if you give the date and time of a cinema showing in Unix time. The current time is 1694599045
So you're saying the confusion of someone visiting a different timezone and not knowing what hour of the clock the sun goes down or comes up is worth avoiding, but the confusion of anyone that has to deal with timezones in any way, such as tv programs, emailing your office overseas, calling your grandma in Ireland, waiting for the release of your new game, wondering what time your aeroplane gets in, etc etc etc is not worth avoiding?
It's not like the sun rises and sets at a consistent time anyway. Not that people have lunch at a certain hour.
A while ago we made a completely arbitrary 'setpoint', and then we've gone and put relatively arbitrary offsets on top of that, and have an arbitrary subset of those offsets change at relatively arbitrary times of the year. It's insane.
Time zones are what let you know whether it's the middle of the night when you want to call gram gram in Ireland. Or are you proposing we all abide the same wake/sleep times and ignore the sun entirely? Who gets the good shift on that clock?
What's a good time to call gram gram is a good example.
She said 10:00.
Option one: Is that my 10:00, or her 10:00, which is 13:00 for me? Is she in daylight savings at the moment? So that would be 12:00 for me, unless we're in that weird period where one of us has started daylight savings and the other is not yet finished theirs, which would make it 14:00 for me? Or is it the other way around, and her 10:00 is my 11:00? Oh wait, she's visiting her sister in Morocco, what's the difference there?
Option two: 10:00 is 10:00, wherever the heck you are, be it down the street, in Greenland, or on Mars.
The clock is only roughly tied to the sun anyway. At the end of December, the sun sets at 8pm in Capetown, but half past three in Warsaw. These places are in the same time zone.
Well time were first laid down because of trains. Every would have there clocks set to 12:00 the sun at or close to its highest point. And that was when a horse was the fastest you could ever travel. Then trains move fast and can just go around each other if they are on the same track. So we had to make times more offical so we wouldn't dispatch trains on collision courses.
People do view TV Channels across timezone boundaries right now.
A lot of folk in the Netherlands and Belgium watch British TV and North America, Australia, Russia etc must have lots of TV channels with audiences spread across more than one timezone.
To say noting of migrant workers/families in various countries who largely shun the local TV channels in favour of satellite/internet TV from their home country. (Indeed the advent of internet TV is making the concept of TV schedules pretty obsolete anyhows)
It still works. You need to know your correction, but it's just like a computer with a slow clock. UTC doesn't explicitly state it, but it's reference is to a non inertial frame, on the earth's surface. (Rotational effects are far smaller than current clock errors, and transmission time errors)