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.

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  1. 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.

    1. Excellent point, Juliet. Thanks for the comment.

  2. Thank you for this clear and useful analysis. It was really well done.

  3. When do we use 12:00 a.m. ? At midnight or at noontime?

    1. My understanding is that it’s never correct to use 12:00 a.m. (or p.m.). Better to use 12:00 noon and 12:00 midnight. And even better to simply use “noon” and “midnight.”

    2. 12:00 a.m. is midnight and 12:00 p.m. is noon

      1. AM stands for ante meridium which is before midday. PM is for post meridium which is after midday. Noon is midday. So neither midnight or midday can be AM or PM. The noon and midnight designations have to be correct or we have been using the wrong Latin designations.

  4. 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?

    1. 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.

      1. I don’t agree that 12pm is unequivocally noon. Why can’t it be understood to be midnight? Noon and midnight are the moments in time exactly between pm and am, so they should be used to avoid confusion.

      2. Noon end the half day. A split second after noon, it becomes afternoon. Afternoon is PM. So 12 at noon is, if you insist on using the Latin terms AM or PM, AM. Otherwise you never end the morning. It becomes 11:59.99999999…….. Once it hits 12, it ends. That first half day is complete. And it is the morning half. AM

      3. When trying to figure out whether a given 12:00 is AM or PM, look at 12:01 following. Is that AM or PM? AM/PM changes on the hour, not at one minute after, so if 12:01 is PM, the preceding 12:00 must also be PM.

  5. 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.

    1. 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?

    2. I prefer no spaces before and after the endash. 1:00 p.m.–3:30 p.m. (The spaces stretch out the time unnecessarily.) Absolutely do NOT use a hyphen in the place of the endash, which means “to.” Now let’s talk about whether to put the periods and commas inside or outside closing quotation marks! :-) (In the USA, we put them inside, but in the UK they go outside. Go figure.)

      1. I agree 100% on the en-dash!

    3. Donn, because it is not just hours and minutes. You have to consider seconds too. If 11:59:59 is AM, then 12:00:01 is PM. It would be weird to have 12:00:00 as AM, but have 12:00:01 become PM one second later. Considering you don’t normally have the seconds displayed, that would mean it would be AM for one second of the clock showing 12:00 but PM for the other 59 seconds.

  6. Is that 9:00 (am or pm) – 10:00 am ? Hmmm… For me the a.m. would clarify the meaning.

  7. These are all great thoughts and there is good reasoning behind this, however it would be very helpful, that , from that first paragraph, another followed explaining in more detail what those findings were prior to the “overthinking” it part. Style guides are different because they are for different purposes/applications and are generally referrenced in publishing. Wouldn’t following an up-to-date style guide be the obvious solution to the problem or question? Further “overthinking” would then have a stronger platform for discussion. Or, at least provide links to where the information for the first paragraph was found since a lot of people really want to know what those are.

    1. Style guides are great and important… and a Google search away. Definitely wouldn’t hurt to include that information or links to them, but I’m looking at things purely from an aesthetic point of view. The “correct” way is important, but not what this article is about. Thanks for the comment!

  8. Great article – thanks! Just one note, it looks like there’s a spelling error:

    “So what do you do? One compromise is to kern the space tighter so it leaves less of a gap.”

    I imagine “kern” is “keep”.

    1. Hey Ryan – thanks for taking the time to comment! “Kern” is actually correct. Kerning refers to the amount of space between letters or characters. So in this scenario, a way to reduce the width of the space between the numbers and am/pm is to tighten the kerning on the ending number and/or the space after the ending number.

  9. Another point is that deciding to omit periods, use lowercase, use a space, and omit minutes will highlight your “am as a word” point to the greatest extent: “1 am” could be read as “I am” depending on the serifs!

  10. I believe the main thing is to be consistent, whatever way you choose to go.

  11. I would prefer omitting the spaces between the number and the a.m./p.m. Furthermore, especially for lengthy summary calendar of events in which page real estate is very scare, I would prefer to use only “a” for “a.m.” and “p” for “p.m.” The readability of the information is diminished only very slightly, but the benefits, I believe, outweigh the drawbacks. Great article, but would have preferred to see at least the mention of the option to use only one letter notations for each half of the day.

    1. Yeah, I think that for long charts/lists, you’re dealing with a whole other animal completely. I could see using just “a” or “p” working in that scenario. Thanks for the thoughts!

      1. Using it in a sentence. Tomorrow at 5:30p we are going to be working there. Saturday at 10:00a we will be at school. but maybe by its self for example Church service
        9:30a – 10:30a
        not sure that works looks kind of awkward

  12. Great article. I used to work for a marketing department at a University and this was always a fight with different departments (thank you style guides for shutting down opinion-based arguments!!!)

    A few personal thoughts:
    • The formatting I use, which tends to work in 95% of scenarios is to keep the minutes, drop the periods, use lowercase letters with no space, and do not repeat the qualifier ( 9:00am singular | 9:00–10:00am | 9:00am–1:00pm). Instantly recognizable as a time given the colon and my eye tends to skim right over the am/pm while still mentally acknowledging its qualification. Adding the space, for some reason, causes my brain to pause and doubling the qualifier just feels clunky, awkward, and unnecessary.

    • Consistency with including minutes or not isn’t always about the one-off piece in front of you but about your (or the client’s) overall branding and “voice”. You shouldn’t really use 9am–10am on one piece and then 9:30–10:00am on another. Pick a style and stick with it.

    • As far as en dashes are concerned, NEVER put spaces between them and the letters/numbers. It’s incorrect formatting and a complete waste of space. Sorry, my biggest pet peeve and personal crusade is the misuse of dash, en dash, and em dash. If I could only have the minutes back in my life from having to scrub those spaces out of people’s Word documents . . . :P

    1. Love your comments, Dan. And yeah, I’m pretty much on board. I’m on the fence about the space between minutes and am/pm. You make a good case for no space. And I’m 100% with you on en and em dashes: no spaces before and after! Ever!

    2. I’ve worked in publishing, press and been a copywriter for 25 years and this is the format I use (unless there’s a specific house style to follow). EXCEPT I would use a dot/full stop rather than a colon, as I would only use a colon for 24 hour clock.
      10-11am, 10.15-11.15pm, 8am-2.30pm and so on. Alternatively 10:00-11:00, 13.15-14.15, 19.25-20:00 etc if 24-hour clock.

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