Why do people write 0:00AM? What does it mean?

Or sometimes they write 0:00PM. Or even 12:00AM. Or 12:00PM. I mean…what do they mean? Is it midnight or noon? I mean, AM means before noon, right? And PM means after noon, right? But 0:00 is midnight. And 12:00 is noon–or midnight. Okay, 0:01AM means something. But 0:00AM? Whichever way you look at it, noon is noon and midnight is midnight! How can you be after noon at noon? It doesn’t make sense. Or before midnight at midnight? Suppose they say: “I’ll see you at 12:00AM on Tuesday.” Now you’re stumped. Is that noon or midnight? And if it’s midnight, is it between Monday and Tuesday or between Tuesday and Wednesday? I mean, really! I suppose logically they must mean between Monday and Tuesday. But it’s not clear! And maybe they mean noon. And I’d hate to turn up at midnight when they meant noon. Or worse still at noon when they meant midnight. Why do they do that?

  • Facio says:

    In the universal parlence, the adapted usage of 12 AM to refer to 12 midnight, while 12 PM to refer to 12 noon are both logically incorrect.. here’s why..

    If the day is divided into two twelve hour halves, and that the first half is refered to in terms of AM, then it is logical to assume that the first half starts with the first second of the first hour and ends with the last second (of the 60 seconds) of the last last minute of the last hour.. In other words, 11:45 AM is basically 11 hrs and 3/4ths of the 12th hour of the first half of the day (the first 12 hr block), i.e. the AM block.. If the first 12 hr block ends with the last second of the 12th hour, then 12 noon, using logic, should be refered to as 12 AM.. (even though it isn’t refered to as such), while midnight, which is the 12th the final completed hour of the second block (the 2nd half) of the day, should be refered to as 12 PM (eventhough it isn’t)..

    So using pure logic, refering to noon (the12hr 00min 00sec of the day) should be written 12 AM, while the 12hr 00min 01sec (just one sec after noon) should be written as 12:00:01 PM (and it is).. Additionally, the 12th hour after noon (midnight) should be written 12 PM.. but the 12th hour 00min 01sec after noon (one sec after midnight), should be written as 12 hr 00 min 01sec AM ( and it is)..

    Therefore refering to noon or midnight as 12:00:00 pm or 12:00:00 am is nonsensical.. just say noon or midnight..

    There is no confusion as to what 12:35 pm refers to and what does 12:07 am mean.. but 12 am to refer to midnight or 12 pm to refer to noon are both incorrect in a litteral sense..

  • Haftor says:

    And chances after every 12 hours^^

  • Haftor says:

    Haha its past and after midnight PM/AM it actually makes alot of sense. Doh

  • Masaya Saito says:

    This is close to the question that I have been wanting to know the answer since I learnt the fact that “12:01AM” means one minute after midnight in English.

    My question is why “zero o’clock” is not used in the twelve-hour system in English.

    In Japan, the twelve-our system is used and there are words corresponding to “AM” and “PM”.
    But, valid values of the hour in Japanese 12hour-system consists of 0, 1, …, and 11. Although the use of 12 is accepted, it is interruptted as an extension of morning/afternoon to afternoon/(next day’s)morning.

    So, I had misunderstood that “AM”
    would mean hours after midnight.

  • jade says:

    i love love love this question. i love the way it was written! lol. because that’s exactly what i was asking and like someone said, it made no sense to my why someone would use pm or am on 00:00 hours.

    i came accross this listing while attempting to research what in the world would someone mean by “0:00 pm”. i am entering a sweepstake online and this is what it says “Participation in the competition is possible from 04/26/2012 until 06/01/2012, 0:00 pm. “.

  • Nucha says:

    Um… I see what you meant ! That’s a problem of as second language learner ,so you will see the problem like this from non speakers often ! As for me ,” I ‘ll see you at 12 Am on Tuesday ” , I understand that I will meet him / her at noontime of the day , can’t mean another meaning .

    As if it means midnight ,00.00 AM should be like that and also if they said 12 PM , it means they don’t understand about time of day by English , so you should explain it for clearing about the matter .

    Good luck !

  • navi says:

    i think everyone got mixed up
    12:00 AM is midnight and 12:00 PM is noon

    it soungs wrong but it is right, i also had problems with this, thats why i know…..

  • Linda k Hollywood says:

    what is the expected out put?what do you see instead?
    *0:00 am and 0:00 are reject or
    *0:00==12.00 am and 0:00pm==12.00 pm

    Linda k (Hollywood)

  • Faeizah says:

    No such thing of 0:00am it should be 12:00am midnight..is it? 😀

  • paula says:

    am=ante meridien
    pm=post meridien

  • nila says:

    does it really matter?
    I suppose usually nothing special would happen at these time!!!!!!!!!

  • Kavita says:

    Dear all
    It is a good time-pass discussion when you folks dont have anything better to do.
    I agree with Gerberth. 12:00 pm is noon and 12:00 am is midnight. This is how we learnt and children are taught all over the world.

  • Me says:

    In my country we never use AM or PM,we only say 00:00 (midnight) and 12:00(midday)

  • bashir says:

    Hey Osama there is no loser around, we are just exchenging our ideas, so feel better out there man,

  • Osama says:

    what a loser

  • fatimah says:

    its really confusing!Everyone seems to have a diffrent opinion.

  • Chaiki says:

    I think we shouldn’t use AM or PM. Just mention 00:00 ( midnight – start a new day ) and 12:00 ( midday )

  • Ian Player says:

    Hey Andy – I think you got mixed up. It should be:

    12:00 PM is regarded as midnight (because it is the end of PM)
    12:00 AM is regarded as midday (because it is the end of AM)

    And another thing. Why did you use the colon? You just said it was confusing 🙂

  • Andy says:

    Use the 24 hour clock 0000 – (forget the colon : it is confusing)

    1200 is midday or noon – (twelve hundred hours)
    0000 is midnight – (zero hundred hours)

    The author uses too much text and it is complicated to read, sorry.

    12:00 PM is regarded as midday (because it is leading into PM)
    12:00 AM is regarded as midnight (because it is leading into AM)

    Keep it simple – just learn this!

  • hanane says:

    Hullo Dear Sir,
    1st of all, let me know whether you are just playing with words to complicate things for us; because there is no difference btw the two:12pm or 00:00pm. 2nd, I think if you opted for a 24 hours time format you will always have the 00:00 shown in your computer’s or mobile’s standby. whereas, if you adopted the am/pm format you will always have an am or a pm added to the written form of a given hour from 1 to 12. so it is up to thee to choose the time format that eases your mind. And let them “they ” write what they want, because it does’t make sense if you bear in mind the destructive activity of time.
    And let me tell you of a verse that i appreciate too much:”so long as man can breathe, so long as eyes can see, so long lives this and this gives life to thee.”
    Are you and teacher Joe one person?????

  • shivani says:

    it is really a good discussion .chilren must be be taught and trained what to use at an appropriate time because time is really important for all of us..

  • Gerberth Castillo says:

    I think the best way to avoid confusion is to write:

    12:00 hrs (GMT) to mean midday, and

    00:00 hrs (GMT) to express midnight.

  • Sharif says:

    When some one points to AM or PM, then he says time in a 12 format, means you cant say 13:00PM (13 belongs to 24 format), of course it is meaningless. but using 0:00AM will logically point to midnight. dont forget to think about seconds. 11:59:59 PM is at midnight and when we use a 12 format there shouldnt be any 12, so one second after that it will be 0:00:00:01 AM, which the last part is one percent of a secont. thus when you think more precisely it’s easy to find out what does 0:00AM mean.

  • Tia D says:

    No, Francisco…
    A.M. means AFTER midnight (and before noon) and P.M. means after noon (and before midnight).

  • languagemokey says:

    When we use the 24 hour clock there is no need to write AM or PM.

    eg. 01.00 = 1 AM, one o’clock in the morning
    17.00 = 5 PM, five o’clock in the afternoon
    23.00 = 11 PM, eleven o’clock in the evening, or at night
    11.00 = 11 AM, eleven o’clock in the morning

    therefore 00.00 = midnight, or twelve o’clock at night

  • Francisco cassongo Mambe says:

    AM:mean befor the midnight,and PM means after noon.

  • Tia D says:

    It is incorrect to write 0:00p.m. The use of 0:00 implies a 24-hour clock system, while the use of A.M. and P.M. implies a 12-hour clock system. Therefore, it is absolutely wrong to use both together.
    The 12-hour clock divides the day into two parts, 12 hours each. The middle of the day (midday) is the twelfth hour, noon, or the meridiem. A.M. refers to the hours prior to midday (Latin: ante meridiem) while P.M. refers to the hours after midday (Latin: post meridiem). Since the meridien is thought to occur right at the exact second of the 12th and 24th hours, it is most common to hear the times referred to as 12 noon or 12 midnight, rather than using a.m. or p.m. However, to be clear, 12:01p.m. refers to the time just after (post) the 12th hour, that is, the first minute after midday (noon); while 12:01a.m. refers to the first minute of the new day, therefore prior to (ante) midday, that is, just after midnight (after the 24th hour of the previous day).

    The 24-hour clock does not need a reference to the middle of the day, the meridiem, which is why the suffix a.m. or p.m. used with this system is completely unnecessary, incorrect, and confusing. So you are wrong to say that “Okay, 0:01AM means something”. It actually doesn’t mean anything at all for the reasons I have given. 0:01 as written implies the 24-hour clock (although it would probably be written 00:01 instead). It refers to the start of the new day. The equivalent in the 12-hour clock would be 12:01 midnight (or 12:01a.m.).

    So if your friends ask you to meet up at 12:00a.m., it should be very clear to you by now that you would be left standing all alone and feeling silly if you showed up at midday, noon, 12:01 p.m., the 12th hour… They are asking you to show up at the first hour of the day, which is just after (or right at) midnight.

  • Muneer Ahmed says:

    well here i want to say that mostely in our soceity many people need to be understand an for that they have set their mind to know that it should be written for understanding and specially for those people its really help who are sitting at home and watching TV they can catch easily the time of their favourite programe.

  • Shirley says:

    Yes, it is indeed a problem. Yet I don’t think people have any misundestanding about that. There are something which grammar can not explain, as people don’t speak according to grammar.

  • Nina says:

    what i understand from this is am(morning) is from 1am(people can say still midnight) to 12am (lunch time) and PM (Noon) from 1300(after luch) to 12pm midnight.


  • bashir says:

    to differentiate goats from sheep is always important, many of us could have an excuse for messing up with time if we would n’t have that better expalantion, no way!

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