On 2023-11-18 11:51, Robert Elz via tz wrote:
12n (or nn or something) and 12mn make much more sense than 12am and 12pm.
The traditional form is "12 m." for noon, where "m." stands for "meridies", i.e., neither ante nor post meridian. This abbreviation is mentioned in (among other places) the Chicago Manual of Style, which goes on to say "very few use that form. And the term 12:00 p.m. is ambiguous, if not illogical." See: https://www.chicagomanualofstyle.org/qanda/data/faq/topics/Usage/faq0061.htm... Computer nerds' strong preference for origin-zero counting have caused computer-based clocks to use 12 a.m. for midnight and 12 p.m. for noon, despite the latter being arguably "illogical". A bit of trivia: in Latin "meridies" also means "south" or "southward", because if you stood in ancient Rome at noon, the sun was in the south. This worked because Rome used local solar time, not mean solar time. Contrast ancient Room to today's Nuuk, Greenland where Stellarium says the Sun's azimuth at local noon today was about 163° and in the summer the Sun's noon azimuth can get down to around 130° - a long, long way from the 180° of true south. In this sense, ancient Roman timekeeping was a whole lot better than ours.