I think folks are averse to "world time" (for reasons, largely inertial), so maybe the baby step is try 1 timezone per country (like China's done for .. 75 years ?).
I'd even argue Local Time has only ~4 useful times: dawn, daytime, dusk, & nighttime. Where I grew up, the parks closed at dusk every day. Nobody complained
If I take a walk at 7:05:35 PM every day, it seems very precise but doesn't indicate whether I need sunglasses or a flashlight. It's meaningless precision, like 0.6235 slices of pizza. If I'm coordinating a walk with you, I might as well use UTC: it still won't tell light from dark, but at least nobody'll be waiting for an hour due to DST. It'd make more sense to schedule our walk at `1 hour before dusk`, or "just" settle for UTC, IMO.
China did that for political reasons. The Republic of China used five, and Russia uses two timezones across those longitudes. Similarly, I also find it quite weird that France and Spain are in CET. France shifted when it was occupied in WWII, but maybe it's justified to remain in CET to reduce friction with the economies of its eastern neighbors. Whatever. Vive la weird. Countries do that to themselves.
A deviation of half an hour from noon is barely perceptible unless you use a sunclock. People can roughly estimate when the sun will set by just looking at local time and considering the current season. What throws a wrench in the works is daylight saving time. I fully agree that DST a huge annoyance and that its benefits were always rather situational.
So You Want To Abolish Time Zones - https://qntm.org/abolish
Being able to express where you are in the 24-hour cycle is useful. That's what local time is: an approximation of the time since the last solar midnight.
To the extent that the approximation is poor, it's an argument for improving it (Spain for example should really set their clocks back an hour), not for getting rid of it entirely.
Besides, Kelvin is the most true temperature scale, not Celsius.
I find this considerably more useful than the Fahrenheit equivalent.
That way you have the "human livable" range kinda between 0-100, which feels very intuitive. Anything above 100ºC becomes effectively unlivable. It also means that it is much easier to distinguish between certain "zones". e.g. saying "70s" or "80s" is easier and more clear than with celsius where you typically are staying within a sliding 10º range from day-to-day.
But why? Knowing the freezing point of water (at sea level, mind you) is only rarely useful to me in daily life. I think the eutectic point of salt and water (that is, the lowest point at which it's possible to cause ice on the roads to melt by adding salt to them) is marginally more useful; this happens to be about -6F or about -21 C. Perhaps it's a bit more important for farmers who need to know whether their crops will freeze overnight, but as a lifelong city/suburbs dweller who knows next to nothing about agriculture I couldn't really say. At any rate, most people are not farmers.
I'm asking this somewhat rhetorically: I don't really care about Celsius vs. Fahrenheit. The pros and cons between the two are so vastly outweighed by the utility of having a global standard that I really wish the US would switch. I'm just pointing out that I don't think that one particular physical property of one particular substance makes for a very strong argument either way.
Or: "below 0C my plants might die"
Or: "below 0C the pond will start to freeze over"
the 60's are warm in the sun and cool in the shade or breeze, the 70's are warm, the 80's are hot and the 90's are really hot, and over a hundred you're looking at death. The 50's you need a jacket, the 40's you need more jacket, the 30's are downright cold and you need an overcoat, and the 20's are frigid.
Celsius has approximately none of those properties. Celsius the 20's encompasses a vast change in comfort level.
https://xkcd.com/1982/ Had it entirely right.
- ex Celsius user