On 2019-09-12 at 06:30, Dan Ritter wrote: > David Wright wrote: >> >> What surprised me is the use of 12am and 12pm in the States. When I >> was at grammar school (in the days of 12hour times), you lost marks >> for writing either of these contradictions. It was either 12 noon, >> 12 midnight, or 12 o'clock (where there's no ambiguity). > > 12 o'clock is the only one of those which is ambiguous. > >> Even more astonishing is the fact that the US Government switched >> their am/pm meanings sometime between 2000 and 2008, which shows >> just how ambiguous they are. > > There is only one sensible interpretation: > > If 11:59 AM is two minutes before 12:01 PM, then 12:00 is PM. > > If 11:59 PM is two minutes before 12:01 AM, then 12:00 is AM. I take a slightly different approach, based on the apparent actual meanings of the words for which "AM" and "PM are abbreviations. It seems intuitively obvious to me that between 11:59 Ante-Meridiem and 12:01 Post-Meridiem must lie 12:00 Meridiem. (Though 12:00:01 - one second later - would be Post-Meridiem again.) Similarly, though less an "obvious necessity" consequence, between 11:59 Post-Meridiem and 12:01 Ante-Meridiem lies 12:00 Midnight. (I understand "meridiem" to be derived from a word which would have literally meant "mid-day".) Both are intuitively represented as "12:00 M" - with no "A" or "P" - and that, in its turn, is ambiguous. That being part of why I stick with 24-hour time whenever possible. > The problem stems from 12 actually indicating what anybody sensible > would consider 0. As is likely part of the reason why the usual 24-hour clock goes from 23:59 to 00:00, yes. -- The Wanderer The reasonable man adapts himself to the world; the unreasonable one persists in trying to adapt the world to himself. Therefore all progress depends on the unreasonable man. -- George Bernard Shaw
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