You have 244 timezones.

Let's have one timezone for the whole world!

You have 245 timezones.

Here’s a hypothetical store in a place where, say, 9:00 is now 23:00 using global time. The store would have been open 9:00-21:00 Mon and Wed, and 10:00-22:00 on Tuesday. But with global time it would look like this:

Mon 23:00 - Tue 11:00

Wed 0:00 - 12:00

Wed 23:00 - Thu 11:00

Not to mention the general headache of having the day change over in the middle of the day every day. “Meet me tomorrow” when tomorrow starts at lunchtime.

Plus, although you’d easily be able to set up international meetings in terms of getting the time right, you will have no idea whether any given time is during work hours in the other country, or even if people would be sleeping. Instead of having time zones you could look up, we’d have to look up a reference chart for, say, when lunchtime is in a country and extrapolate from there. Or imagine visiting a country and you need to constantly use a reference guide to figure out the appropriate time for everything throughout the day.

Books that reference time would all be specific to their time “zone”.

It would make so much sense to have a universal time that everyone can refer to for that use case of wanting to schedule things. And, in fact, UTC already exists.

As much as time is a constant thorn in my side, both time and timezones are a necessary evil.

Others have outlined some of the issues regarding time zones and the abolishment of them so I won't get into that. What I will say is that time keeping systems generally don't track time in your local timezone. Technology has long since given up on local time as a measurement. Almost all system clocks for computers, phones, pretty much anything electronic, is almost always stored in UTC, or a time code based on UTC.

And I can hear it now, someone saying " but the time on my $thing is $correctlocaltime, which is not UTC"

Yep, and that's where the magic happens. While the time is stored as UTC, it's displayed as local based on your device's time zone settings. In some cases, like with cellphones, the local timezone is set by GPS. The device gets a very very general idea of where you are from GPS, and sets your timezone appropriately. Windows will do this too based on location awareness, by default. I'm sure os x also does something similar.

When the time is displayed it takes the UTC system time and filters it through the UTC offset based on your timezone, and displays local time, factoring in daylight savings, if applicable.

We've silently converted to a single unified time globally, and nobody realizes it has happened because the user interface shows you what you want to see.

Do you really wanna live in the part of the world where sunrise happens at 2pm?

Grateful for this thread. Never thought about how its actually useful to have different zones to know whether to call or other things. Kinda makes a lot of sense

I use UTC for all of my logs. Keeps it less confusing.

That would make 9 to 5 jobs quite a challenge outside Europe and Africa...

You could address Daylight Savings Time by just having people set their own schedule, but it was generally seen as easier for the government to change the clocks.

As others have mentioned, there are typically schedules that are assumed based on time. It is easier from a social setting to keep time universal and adjust based on time zones. The context informed by local time is fast more useful than a standard time.