What A.M. and P.M. Stand For

Sun ClockToday I found out what a.m. and p.m. stand for.

And no, it’s not, as my first grade teacher told me, “After Midnight” and “Past Midday”. LIES!!!  Though, funny enough, not really that far off the translated versions of the Latin words for which a.m. and p.m. actually do stand for.

It turns out, a.m. stands for “ante meridiem”, which is Latin for “Before Midday”; p.m. stands for “Post Meridiem”, which is Latin for “After Midday”.

Interestingly, this finally clears up for me one of the interesting quirks of the 12 hour clock system where time counts from 12 a.m. to 1 a.m. and likewise goes from 11 a.m. to 12 p.m., which always seemed odd, but now makes perfect sense given what a.m. and p.m. stand for.

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26 comments

  • Since midnight and noon are the meridiems referred to, it is my understanding that the two are neither AM nor PM, they are just 12:00.

  • Interesting info, and when referring to 12:00, I usually write it as either “noon” or “midnight” vs 12:00pm and 12:00am, or 12 noon/midnight. I still get confused which is which!

  • dalanda derouiche

    i was very astonished how you’ve just discovered the abbreviations a.m and p.m now, i’m arab, i study english as a third language (french is my 2nd language) and our teachers taught us the true full words. and you (english speaker) you’re wrongly taught???????how strange

    • Not so strange, whenever we take the language for granted and assume our own answers are the right ones.

  • Now it’s finally clear to you what 12:00 a.m. is? There’s no such animal. There is only one meridan and that is noon. Midnight is neither a.m. nor p.m. and neither is noon. It is much more clear and correct to use n. or nn. and m. or mn.

  • AM and PM are both confusing and long. Americans like to stick with inconvenient measures. Look at all the imperial metrics they still use – terrible! The 24h clock is so much easier. 14:00 vs 2:00 PM – no possible confusion and shorter. Otherwise the military wouldn’t use it :)))

  • As a kid in school one of my classmates taught me an easy way to remember which is AM & PM. When the alarm clock goes off in the morning (usually too damn early); what’s the first thing out of your mouth? “Aaaaaaaagghhh!: There you go – A for mornings. When I asked my classmate what the P in PM stood for; he said “Piss all”.

  • 12:00 p.m. And a.m. don’t actually exist because you can’t have a midday that is before or after itself. So that’s why we say noon instead of choicing if it’s an a.m. or p.m. Which also means we say midnight since we don’t have one for noon.

  • While I understand the argument of 12:00 being neither am or pm, I think it’s perfectly acceptable to say 12:00 PM for noon and 12:00 AM for midnight as these both start the next 6 hours of the phase.

  • One day I asked my brother what a.m. and p.m. Mean he said well how I remember it it’s at morning and passed morning

  • One more thing is you should not add dots “.” while using latin shortcuts. AM instead of A.M. and PM instead of P.M.
    Same goes for eg, ie, etc.

  • Interesting fact, the English/Scottish/Welsh/Irish druids believed the day began @ 1201am & ended @ 1201 pm, as a death/rebirth of the sun. (from darkness to light, from light to darkness. The rise of the sun at the moons fall, & vise versa)

    • Non off ya business

      Then what the heck would 1202 pm through 1200 am be? Does time just stop for a few hours every day?

  • You say: “Interestingly, this finally clears up for me one of the interesting quirks of the 12 hour clock system where time counts from 12 a.m. to 1 a.m. and likewise goes from 11 a.m. to 12 p.m., which always seemed odd, but now makes perfect sense given what a.m. and p.m. stand for.”
    I dont get the overlap??
    And I was never taught what you said that’s, sad – but not NEARLY as sad as the demonic agenda being taught today!

  • Its convoluted. If am means before midday then 12 am means midnight; means 12 hours before midday, ok this is correct. But 1 am means 1 hour before midday?

  • I think you contradicted yourself when you said “Lies” about your “teacher” telling you that it meant “after midnight ” and “past midday”.

    Before Midday and After Midday is basically the same difference…
    Is it not?

  • A.M. and P.M.

    The terms *A.M.* and *P.M.* have a *Sanskrit* connotation and not English as is easily assumed.
    In English parlance the term A.M. means ‘ante-meridian’ and P.M. means ‘post-meridian’. But the question remains who is ante-meridian and post-meridian? That is to say the subject himself is missing. The ‘Sun’ who is vital to the calculation remains un-mentioned. This is unthinkable and unjustifiable.
    That lacuna arises because it is not realized that the letters A.M. and P.M. are the initials of the hoary Sanskrit expressions *(आरोहणम् मार्तडस्य्) Arohanam Martandasaya* (i.e. the climbing of the sun) and *(पतनम् मार्तडस्य्)Patanam Martandasaya* (i.e. the falling of the sun).

  • For those who are confused by the “midnight” and “noon” pieces, here is how the day is divided if you are using the 12 hour clock system. In the West, a day officially begins at midnight. (Picture New Year’s Eve if you are not sure of that.)

    12 midnight
    12:01 am to 11:59 am (the time between midnight and noon)
    12 noon
    12:01 to 11:59 pm (the time between noon and midnight)

    A couple of other notes:

    Partha: The term is “meridiem” not “meridian.” An easy way to remember this difference is to think of “Carpe Diem!” (Seize the Day!) “Diem” means “day” in Latin.

    Iliyan: About the 12 hour clock system, this is how cultures go. We each have our approaches, and historical bases for them. And yes, the 24 hour clock system is unambiguous. But in the US, we are still using the 12 hour clock system in numerous contexts, so it is good to clarify the a.m., p.m., noon and midnight terms.

    Marc: What is the authority you are citing for not using the period after abbreviated Latin words? (e.g., etc., a.m., p.m., i.e., et al.)?

    It seems the convention is to put a period if the Latin word is abbreviated, but not if it isn’t.

    Here are some examples:

    etc. is the abbreviation for et cetera (and the rest). The abbreviation puts the whole word et and the first letter of cetera together.

    a.m. is the abbreviation for ante meridiem (before the midday point)

    e.g. stands for exempli gratia (for the sake of examples)

    i.e. stands for id est. (that is)

    Et al. There is no period after et because et is a whole Latin word (and) but al. has a period because it is an abbreviation of the Latin word “alia” (others).

    Can you provide a source for your suggestion that we dispense with the periods signifying abbreviation? I think most editing style guides support using the period with abbreviations.

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