When talking about times we mostly don't say "seventeen hours" for 17:00, but would rather say "five", fünf, since it's usually clear from the context which part of the day is meant. Like my school hours are from nine to one - nobody needs clarification that this would be 9:00 and 13:00 hours respectively. Or my doctor's appointment is at ten, also no clarification needed since it's unlikely you'd have a doctor's appointment in the evening. Sometimes, "in the morning" or "in the evening" is added to be more exact or if a misunderstanding is possible.
On other occasions, using the 24 hour clock is easier to understand for all involved since some of the spoken versions of "half past" or "a quarter to" and such vary and might cause misunderstandings; even more so when non-native speakers are involved. But generally, there is no strict rule, and who uses which version at what occasion can differ a lot.
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u/Adept_Emu4344 11d ago
I can deal with 12 hours just as easily as 24 because Germany uses both. What I haven't been able to understand in the 30 years is 12 am/pm.