Noon and Midnight: AM or PM?

Is noon a.m. or p.m.? Well, the correct answer may surprise you because it is actually neither. That’s right; technically noon is neither a.m. nor p.m. Although it is common to see noon expressed as 12:00 p.m., it is actually incorrect. So the next time one of your friends sends you an email saying, “Let’s meet at 12:00 p.m. noon for lunch.” you might want to take note.

In this post, I want to talk about the time designations for noon and midnight, but brace yourself because this is a tricky one.

Is Noon AM or PM?

is-12-noon-am-or-pmThe reason why noon is neither a.m. nor p.m. has to do with the meaning of these two abbreviations. The abbreviations “a.m.” and “p.m.” are short for the Latin terms “ante meridiem” and “post meridiem.” These terms literally mean before noon and after noon. For example,

  • I ate breakfast at 9:00 a.m. (before noon)
  • I got home from work at 6:00 p.m. (after noon)

This is why “noon” can neither be a.m. nor p.m. because “noon” cannot be “after” or “before” itself. You can, however, express noon by saying 12:00 m. (meridies), but very few people use this form and it may even add to the confusion.

Is Midnight AM or PM?

What about midnight? Is midnight a.m. or p.m.? Well, based on our previous descriptions, you might think that midnight could be called 12:00 a.m. since it is 12 hours before noon. But, in some sense, it is also 12 hours after noon, seeing as the 12 hours preceding it carry a “p.m.” For instance, 11:59 p.m. So, which is it? Well, that depends on which day midnight is a part of, the one that is ending or the one that is beginning (more on this below).

Midnight, as I say above, is 12 hours after noon of the current day, but technically it’s also 12 hours before noon of the next day. The problem is that midnight cannot be unambiguously referred to as a.m. or p.m., so we avoid them altogether. The convention, however, (as is the case with digital clocks) is to display midnight as 12:00 a.m.

All of this confusion leads style guides like the AP Style Guide and the Chicago Style Manual to forbid using numerals (12:00 p.m. and 12:00 a.m.) when expressing noon and midnight.

Instead of saying 12:00 p.m. or 12:00 a.m., it is best to simply stick with calling the times “noon” and “midnight.” This way you can eliminate any confusion between the “a.m.” and “p.m.” debate. It should also be noted that saying “12:00 noon” or “12:00 midnight” is not necessary and possibly a bit redundant. Consider the following sentences,

  • Wrong: Let’s meet for lunch at 12:00 noon.
  • Correct: Let’s meet for lunch at noon.
  • Wrong: I should really go to sleep before 12:00 midnight.
  • Correct: I should really go to sleep before midnight.

The numbers are not needed because “noon” and “midnight” communicate all that is needed.

Does Midnight Begin or End a Day?

Did you raise an eyebrow above when I said that midnight is 12 hours after noon of the current day? Does this mean that midnight is the end of a day—or is it the start of a day?

Good question.

There is some additional confusion that arises when we try to understand how this word “midnight” is applied to dates. For instance, if I asked you to meet me Monday at midnight, would you meet me early Monday morning or late Monday night? That is to say, is midnight a part of the day that is ending or the day that is beginning? The AP Style Guide and the New York Times Manual of Style both hold that it is the former. So according to these style guides, you would be meeting me late Monday night. This means that the exact moment of midnight belongs to the day that is ending. It isn’t until 12:00:01 that the new day has begun, despite what you digital clock says.

Military time has a much more clear solution to this problem in that they created a new time designation to avoid ambiguity. Military time uses 2400 when referring to midnight belonging to the day that is ending. It uses 0000 to refer to midnight belonging to that day that is beginning.

So from the example above, if I asked you to meet me Monday at 2400h, we would be meeting late Monday night as it approaches Tuesday. If I asked you to meet me Monday at 0000h, we would be meeting early on Monday, right after it changes over from Sunday.

To summarize,

  • Noon is neither a.m. nor p.m.
  • Midnight is a part of the day that is ending, not the day that is beginning.
  • When expressing times for “noon” and “midnight” it is best not to use numerals (12:00 a.m. and 12:00 p.m.).
  • Avoid the redundant 12:00 noon and 12:00 midnight.


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