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:

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".