AM or a.m., PM or p.m.: Do I Capitalize AM and PM?

When emphasizing an exact or precise time, the abbreviations “a.m.” and “p.m.” are used. These two abbreviations stand for the Latin terms “ante meridiem” and “post meridiem,” which literally mean before noon and after noon.

AM and PM as Lowercase Letters

There are a few generally accepted ways to write these abbreviations in your writing. The first and most common way to write them is with lowercase “a.m.” and “p.m.”

This way requires periods, and both Chicago Style and AP Style recommend this way of writing the abbreviations.

  • This subway train will leave daily at 10:05 a.m.
  • After 10:00 p.m. I really need to sleep.

AM and PM as Small Capitals

Rather than using the lowercase method, the abbreviations can also be written using small capitals. This way can be written with or without periods. For example, both of the following are acceptable,

  • We will meet for lunch Tuesday at 10:00 AM.
  • We will meet for lunch Tuesday at 10:00 A.M.

Given that is acceptable to write “a.m.” and “p.m.” a couple of different ways, you should always make sure that you are being consistent. Pick one way and stick with it.

For example, you should never punctuate a sentence as follows,

  • I leave for work at 8:00 AM and get home at 6:25 p.m.

Instead, it should be written in one of the following ways.

  • I leave for work at 8:00 a.m. and get home at 6:25 p.m.
  • I leave for work at 8:00 AM and get home at 6:25 PM.
  • I leave for work at 8:00 A.M. and get home at 6:25 P.M.

Putting Small Caps Into Microsoft Word

What are small capitals? Not many people know what they are. Small capitals are simply uppercase (or capital) letters that are set at the same height and weight as lowercase (or small) letters. For example,

  • AM PM, AM PM , a.m. p.m.

The first “AM PM” is all caps. The second is small caps. The third is lowercase.But how do you put these into Microsoft Word?Well, it is actually pretty easy, and there are a few different ways.

The easiest way to do it is to highlight and “right click” the text that you want to change to small caps. After you do this, click “font” and a window will appear. You will then see a box that says “Small caps.” Click this box and then click “OK.” Your text will then change into small caps. You can use this same method if you are using a Mac. You can also click the “Small caps” button on your formatting palette, and it will change the font into small caps.


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