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What do a.m. and p.m. stand for when talking about time?

Callithumpian
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nicholas ainsworth
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1 Answers1

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They are from the Latin for ante meridiem and post meridiem, which mean "before noon" and after noon", respectively.

snumpy
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    It is worth mentioning the crazy gotcha involving 12am and 12pm. 12pm means noon and 12:30pm is the half hour after noon. 12am means midnight. Many, many, many people get this incorrect. – MrHen Apr 05 '11 at 20:36
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    @MrHen; The confusion is usually caused by the fact that 11am is directly followed by 12pm, or 12pm is directly followed by 1pm, rather than that 12:30pm follows 12:00pm. But otherwise you're correct, it's a common mistake. :) – falstro Apr 05 '11 at 20:56
  • @all: Probably flirting with off-topicism here (I only got here from a link on Discussion re trivial questions), but I think MrHen's point could well be useful to a number of future 'seekers after knowledge' who might not have realised they were in danger of getting it wrong, and therefore might not have actively sought the additional info. In short, I don't see why OP should be rejected as 'trivial'. – FumbleFingers Apr 05 '11 at 23:41
  • Trying deperately to stay on-topic, I'll just say the standard rule is Midnight belongs to the new day, and woe betide any programmers, schedulers, etc. who get that wrong (but a surprising number do). – FumbleFingers Apr 05 '11 at 23:44
  • The confusion between 12am and 12pm is sufficiently commonplace that legal documents often use times like 12:01pm to make it clear. For example: All contest entries must be received by 12:01pm on April 1, 2012 to be considered. – Wayne Johnston Apr 06 '11 at 02:44
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    If you're worried about confusion, you can just say 12 noon or 12 midnight. – Peter Shor Apr 06 '11 at 03:30
  • @Wayne Johnston: how does it help? – Louis Rhys Apr 06 '11 at 06:22