I wonder how you denote the midnight in case when you use the system with a.m. and p.m. Would the midnight be 12 a.m., or 12 p.m., or both?

  • 2
    In any language, midnight is 12 am. Noon is 12 pm.
    – fixer1234
    Mar 24, 2017 at 8:33
  • As a night owl, I'm sure that it should be "12 a.m". Mar 24, 2017 at 8:43
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    @fixer1234: your answer may be technically true, but many people seem to find 12 AM or 12 PM confusing. Even the Latin is confusing, since Ante Meridian means before midday and Post Meridian means after midday. How can noon be before or after midday? And midnight is both before AND after midday. I find it much less ambiguous to use 12 noon or 12 midnight rather than using 12 AM or 12 PM to describe those times. Or use 12:01 am or 12:01 pm. One minute difference is better than 12 hours off. Mar 24, 2017 at 8:45
  • @MarkRipley, I don't know the historical basis, but I suspect it might simply be convention. Times on the border have to be assigned to one side or the other. In "military" time, there is no 2400. Midnight is 0000 and the start of a new day, which makes it AM.
    – fixer1234
    Mar 24, 2017 at 16:42
  • 2
    sigh another reason to get rid of AM/PM altogether. Can't Trump do something useful and forbid their use?
    – Glorfindel
    Mar 24, 2017 at 21:00

1 Answer 1


Of course, "midnight" means 12 a.m . It means nighttime, not daytime.

  • This is circular reasoning. The question isn't about daytime vs. nighttime, it's about the basis for associating AM or PM.
    – fixer1234
    Mar 25, 2017 at 2:22
  • 1
    "of course"? This is the most illogical thing I have ever witness in English, I'm not kidding. How do you explain that after 11 pm it's 12 am and not 12 pm? Jun 29, 2017 at 14:30
  • 12 a.m. makes sense. 12 p.m. doesn't make sense at all. That should be 12 m. as it's neither ante nor post meridiem., it actually is meridiem.
    – csabinho
    Nov 9, 2023 at 11:16

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