I am from the USA and whenever I travel to Europe (Poland, Germany, England, Scotland, etc.) I never quite grasp whether 24h is used for all purposes, or just "official" purposes (like train schedules) while casual conversation remains 12h. I wonder if the young/old divide you described is prevalent in most places.
I assume some people (perhaps older people) wear analog 12h wrist watches, and wouldn't translate to 24h after looking at it to answer a random question "what time is it?"
Interesting! It sounds like maybe there are more people doing +12 mental math (reading analog clocks in 24h places) than people doing -12 mental math (Americans trying to read 24h times) even though the USA is always the "weird" one.
That probably indeed varies a lot by location and demographic.
In my experience in Finland, casual spoken discussion is usually 12h but written is 24h. The xx:xx format always means 24h, whether written or spoken.
When referring to a precise minute 24h is common even when spoken - "train leaves at sixteen thirty-four" - the 12h alternative is "train leaves at four past half five" or "twenty-six to five".
Notably, one would never say "four thirty-four" as that refers to 04:34 (24h).
Also, 12h is used when casually written with letters - e.g. it would be "meet you at three" / "nähdään kolmelta", not "meet you at fifteen" / "nähdään viideltätoista".
> In my experience in Finland, casual spoken discussion is usually 12h but written is 24h. The xx:xx format always means 24h, whether written or spoken.
My exact experience in France as well. “Six heure du matin” for example.
I assume some people (perhaps older people) wear analog 12h wrist watches, and wouldn't translate to 24h after looking at it to answer a random question "what time is it?"