It’s extremely common in Europe. I regularly get messages with “15h”, “22h”, etc, but spoken is a bit of a mixed bag, you can usually use 12 hour time and know if it’s AM/PM from context, but sometimes you need to be specific.

Though the weirdest thing I’ve had to learn in Germany about time is, near where I live it’s common to say “one/three quarters [hour]”, instead of “quarter past/to [hour]”, so 10:15 is “one quarter 11”, and 10:45 is “three quarters 11”. It makes a little more sense when you know that “half 11” mean “half to 11”, not “half past” like is typical in English.

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.

What is the logic for distinguishing 12AM vs 12PM? Also, you have double of every element and need 2 more sillables each to distinguish.

It's confusing and inefficient.

AM/PM requires you to change the value order of numbers in your mind: for the same calendar day, hours are, in order: 12-01-02-...-10-11 AM, 12-01-02-...-10-11 PM.

In Poland we use both interchangeably. U can use whatever suits you and everyone knows just fine.