You are trolling, right? Like, majority are using 24h.
Disclaimer: generalizations from personal experience.
Some nations use 12h with “at the morning” or “in the evening” in casual verbal conversations. In formal conversations it’s always 24h clock. Just yesterday I was booking an appointment at reception and they proposed me 14:45, so 24h clock, even though it is obvious that place is closed at 2:45 AM. But AFAIK some don’t use 12h even in casual speech, like Germans. Maybe Germans can confirm here.
I think it’s language thing, I never heard of “AM/PM” in language other than English. If you want to tell time in 12h clock it’s usually period of the day, like “2, at night”, “6 in the morning”, “10 in the evening”, which is much more cumbersome than just 2, 6, 22. And imagine it in writing.
Well, I hope you are sleeping. So technically your day starts at <put whatever time you’re getting up>.
0th hour should start at 6 AM or something. But I better stop thinking about how dumb clocks and calendars are