The Grammarphobia Blog

Is noon 12 AM, 12 PM, or whatever?

Q: The parking signs in my town refer to noon as 12 PM. Since “PM” stands for “post meridiem” (“after noon” in Latin), can 12 PM be used for noon itself?

A: The simple answer is yes, but I’d advise against doing it. Traditionally, the term “12 PM” is used for noon in countries like the US with a 12-hour clock.

For those who argue that noon and midnight are neither AM nor PM, I can only cite the American Heritage Dictionary of the English Language, which has the following Usage Note with the entry on PM:

“By definition, 12 a.m. denotes midnight and 12 p.m. denotes noon, but there is sufficient confusion over the meaning of a.m. and p.m. when the hour is 12 to make it advisable to use 12 noon and 12 midnight where clarity is required.”

I agree that “12 AM” and “12 PM” are confusing and should be avoided, but I would argue that “12 noon” and “12 midnight” are redundant. Why not simply say “noon” and “midnight”?

You may be interested in knowing that “meridiem” actually means midday in Latin, and that the terms “noon” and “midday” have not always been synonymous in English.

As the Oxford English Dictionary points out, the word “noon,” dating back to the year 900, originally meant “The ninth hour of the day, reckoned from sunrise according to the Roman method, or about three o’clock in the afternoon.” By the 14th century, according to the OED, the word “noon” had come to mean 12 o’clock.

Although dictionaries usually define “midday” as middle of the day or noon, it’s often used more loosely than the word “noon.” The entry for “noon” on Wikipedia, for example, describes midday as “the period of early afternoon, beginning at noon and lasting until mid-afternoon.”

Well, I think that’s enough noon-sense for now.