Heh thanks for explaining it, I never knew if noon was 12am or 12pm. In German we say "11 in the morning", "12 o Clock (noon*)" , and "1 o Clock (in the afternoon)"
But typically we don't say whether it's am or pm, it's clear from context if "i need to be in the work meeting at 9"
Clocks, TV listings, my work timesheet read 24h times. We read 15:00 as "three" most of the time.
Btw some software tools (my timesheet for work) differnciate between 0:00 and 24:00. I can work (theoretically) from 0:00 to 8:00 (8h in the night to morning) and from 16:00 to 24:00 (8 hours from afternoon to midnight).
So 0:00 and 24:00 are the same moment but thought to belong to the next or previous say, respectively.
Because 12 and 60 are great numbers to divide. You can take a half of it, a third and a quarter and still get whole numbers.
Iirc the French did try decimal time at one time, it was not convenient.