How to Write AM and PM

The best way to write AM and PM in times

This article is not about the correct way to write AM and PM. I did a quick internet search and found all kinds of answers. There are some style guides that are very specific in their answers, but those specific guidelines change from one guide to another. The general consensus I’m seeing is that it’s up to taste. With that in mind, this article is about which way is most pleasing to the eye and easiest to read. Let’s get to it.


Using periods in AM/PM

We’ll start with the issues of periods. AM and PM are common and everyone understands they are abbreviations. If you put a period after each letter, that’s a total of four characters. When writing a single-digit hour such as 9:00 a.m., that’s the same number of characters as the time itself and is too much real estate for the task at hand. Granted, it is true that including the periods takes away all doubt as to the purpose. And that’s important given the fact that “am” is an actual word outside of time designation. So while I don’t fault anyone for using periods, I find they feel old-fashioned and unnecessary. Skip the periods, especially in lists of times or series of times.


Using capitals for AM/PM

Next up is the issue of capitalization. Do you capitalize both letters or make them both lowercase? If you’re talking about AM and PM, you will probably want to capitalize them, as I have been doing. After all, as mentioned previously, “am” is a word all its own. You could make them bold or italic, but they should be set apart in some fashion.

However, our focus is on their use when placed after a time. Which is better, 2:00 PM or 2:00 pm? I find that 2:00 PM feels too chunky. Again, given it’s role as a qualifier, the capitalized letters are too prominent. When placed after a double-digit hour, like 12:00 PM, it’s not as bad—but it’s still very glaring. And if you skip the minutes and just type 2 PM, you’re left with a clunky set of characters.

Note that while I prefer lowercase over uppercase, the best solution is to use small caps. This provides the best of both worlds, setting the designation apart from other text better than lowercase does, while not drawing the unneeded attention that uppercase does. But the fact remains that few fonts offer this style, and therefore it’s rarely an option.


Using spaces with AM/PM

What about spaces? Do you include a space between the time and the AM/PM? My answer to this is not black and white and you’ll soon understand why. When written with the minutes, I find 9:00pm and 10:00am are simply too busy. They form a long string of numbers and letters (plus a colon) which give birth to one unwieldy chunk of text. Running them together is rarely the way to go. I definitely prefer 9:00 pm and 10:00 am.

But what if you skip the minutes? Do 9pm and 10am look best or are 9 pm and 10 am the way to go? Skip the spaces and they feel very squished. But you may just as well argue that including a full space between looks too disjointed. The two parts feel like separate entities as they’re too far apart.

So what do you do? One compromise is to kern the space tighter so it leaves less of a gap. That can be a great option and one to seriously consider when typesetting a headline or any large display. But for body copy and website copy, few people are willing to invest that much time and attention.

Here is my answer to this conundrum. Both solutions are troublesome. So why use either one? Skip the issue altogether by using a better format—this leads right into our final issue.


Formatting for AM/PM

Consider the format of the time portion. Do you include the minutes even when the minutes are zero and are not needed? This comes down to readability, comprehension, and professionalism. The simple answer is that including the colon and minutes is almost always going to be the best way to go. There are three reasons:

  • First, 7:00 pm is instantly recognized and processed as a time. The alternative of 7 pm is less so. You may argue that point by saying both are equally recognizable since “pm” is included after each one. But take that away and the point becomes clear that 7:00 is more easily understood than 7.
  • Second, when the qualifier (pm) takes up more space than that which it qualifies (a single-digit hour), it feels a tad backward.
  • Third, skipping the minutes looks unprofessional.

In conclusion, a lot of this comes down to taste and I’ve explained my opinion. But the one thing I see many people do that I insist is bad design across the board is using multiple formats in the same sentence or layout. An event should not start at 9 am and end at 2:30 pm. If one time includes the minutes, all times should include the minutes. The event runs from 9:00 am to 2:30 pm.


  1. Juliet Macan

    Thanks for the summary, revising some texts, I was in a quandary and did similar research that left me unsure. I agree with you conclusion and would like to add a reason for keeping the space and eliminating the periods: translation and especially computer assisted translation work better when the number is separate from the qualifier and can thus be updated (if necessary) automatically; similarly, the period is usually considered a “sentence” divider.

  2. Marrie Immaculate

    Very grateful for this insightful lesson. As a matter of fact, I have just received an invitation to watch a live video at 12pm, now I have to ask the sender whether that will be day or night. Btw, is it invitation or invite?

    • Mark

      As Lynn pointed out above, 12pm is unequivocally noon. If your friend intended to invite you to a showing at midnight, he or she has listed the wrong time.

      Formally, “invite” is properly used only as a verb and “invitation” as a noun. Your friend may invite you to an event, but what you receive is an invitation. However, the brevity of textspeak and the advent of variations such as “evite” often contradict this rule, and it is becoming increasingly popular and acceptable to use “invite” as a noun.

  3. Mark

    Overthinking this further, if a time span falls in the same half of the day, is it preferable to put the time designation only at the end, or after each? Or should context dictate?

    9:00 – 10:00 am
    9:00 am – 10:00 am


    P.S. personally, I think it’s more elegant and readable to use the en dash with a space on each side rather than “to” when designating a time span.

    • Jason Horst

      Hey Mark. Definitely agree on the en dash over the word “to.” But as to your main question, that’s a tough call. Leaving the time designation off the first one looks awkward, but including it on both seems a bit overkill. I’d lean toward including it on both. Usually common sense makes it unnecessary—but I’ll side with thoroughness over awkwardness. Great question! What do you think?

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