# Midnight, noon 12am, 12pm?



## timpeac

What time of day is 12AM. Is it midnight or midday?

I was talking with people at work about this, and not everyone agreed.

It suggests midnight to me, but I think that it is ambiguous.


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## mjscott

I agree with YOU, timpeac. 11:59:59 (or 23:59:59 nautical time) is PM--but when you hit 12:00 a.m. you have started your new day--date-wise.


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## Jana337

An opinion from a most authoritative source:

AM and PM start immediately after Midnight and Noon (Midday) respectively.

  This means that 00:00 AM or 00:00 PM (or 12:00 AM and 12:00 PM) have no meaning.

  Every day starts precisely at midnight and AM starts immediately after that point in time e.g. 00:00:01 AM (see also leap seconds)

(...)

   It is after Noon that PM starts e.g. 00:00:01 PM (12:00:01)


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## Cath.S.

PM means_ post meridiem _("after midday" in Latin) and AM means _ante meridiem _("before midday").

Therefore 12 PM, _12 after midday_ in other words, is necessarily midnight.

So 12 AM _is _midday, then, right?

Wrong, 

12 AM, "12 before midday", is a contradiction in terms, as midday cannot be before itself, so 12 AM should not exist at all, in fact.

Edit
Jana, I hadn't seen your post as I was still plodding along with mine.


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## timpeac

Good points Jana/Egueule, it's no wonder we couldn't come to an agreement in the argument we had in the office then if the terms are inherently ambiguous. It was amazing though how "clearly" it seemed to some people that it must be one, whereas it was just as "clearly" the opposite for others. You two brain-boxes spoilt the fun before the arguments could begin!!


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## daviesri

12am is midnight

12pm is noon


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## timpeac

daviesri said:
			
		

> 12am is midnight
> 
> 12pm is noon


 
Thanks for clearing that up, but it might be good if you could add your evidence.


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## Jana337

timpeac said:
			
		

> Good points Jana/Egueule, it's no wonder we couldn't come to an agreement in the argument we had in the office then if the terms are inherently ambiguous. It was amazing though how "clearly" it seemed to some people that it must be one, whereas it was just as "clearly" the opposite for others. You two brain-boxes spoilt the fun before the arguments could begin!!



To err is human, but not in this forum. 

Jana


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## Cath.S.

Jana337 said:
			
		

> To err is human, but not in this forum.
> 
> Jana


Good one, Jana!


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## daviesri

timpeac said:
			
		

> Thanks for clearing that up, but it might be good if you could add your evidence.


 
That was what I was always taught.  Since you asked for evidence it seems that I have been misinformed all of these 40+ years.  It seems that you can use either one for either time because of the definition of each.  My vocabulary from now on will only use 12 noon and 12 midnight.


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## Jana337

Wiki has more. Its comments on the usage in the USA bear out what Daviesri asserts.

Jana


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## timpeac

daviesri said:
			
		

> That was what I was always taught. Since you asked for evidence it seems that I have been misinformed all of these 40+ years. It seems that you can use either one for either time because of the definition of each. My vocabulary from now on will only use 12 noon and 12 midnight.


 
Thanks for adding that. I'm sure you can see that it is always helpful to add why you think something, because that then allows others to also make a judgement on how much credence to give the opinion. Even "this is what I taught" is evidence, not the strongest because of course your teacher might themselves have been ill-informed (it can happen!) but at least it gives the basis on which you make the assertion.


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## Jana337

egueule said:
			
		

> Good one, Jana!



It's my upbringing. 

Jana


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## lsp

The first time I saw this same subject in the forums I was surprised, but here it is again!


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## timpeac

lsp said:
			
		

> The first time I saw this same subject in the forums I was surprised, but here it is again!


 
Well I absolutely positively swear I searched before posting this!! (I searched for "midday".

Ah, I've just checked. The thread you are referring to _did_ come up but since it was called "my boss and I" I didn't think it was relevant. Since we can't be expected to read every thread that comes up on a search to check the subject hasn't already been discussed this neatly shows the need to add relevant subject titles to our threads!!!

So don't admonish me mods!!


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## lsp

timpeac said:
			
		

> Well I absolutely positively swear I searched before posting this!! (I searched for "midday".
> 
> Ah, I've just checked. The thread you are referring to _did_ come up but since it was called "my boss and I" I didn't think it was relevant. Since we can't be expected to read every thread that comes up on a search to check the subject hasn't already been discussed this neatly shows the need to add relevant subject titles to our threads!!!
> 
> So don't admonish me mods!!


I didn't mean to admonish you either, timpeac.  I coincidentally remembered something about it or I would never have found it. I agree about thread titles and this is precisely why it's a good rule, though we are better now than we used to be!


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## leenico

Jana337 said:
			
		

> Wiki has more. Its comments on the usage in the USA bear out what Daviesri asserts.
> 
> Jana


See Jana, we agree on some things.


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## irishstu

I've always been taught that 12am is midnight, but I see now that both seem to be possible. 

Interestingly, I've recently had a similar issue crop up on a manual I was writing for setting a video recorder to start a recording at midnight. The clock is 24 hours, which makes it easy, in that midnight is 0:00. The problem is knowing which DAY it refers to.

An example. The TV schedule says that my favourite program is on 31st May and starts at midnight that night. I set the recorder to start at 0:00 on 31st May. Does it start at the END or the BEGINNING of that day? I'd say the beginning (so in fact I'd have to change the date to 1st June to get round this), but I think some people might disagree.


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## te gato

I have also been taught that 12am is midnight..(or the witching hour)...and that 12pm is noon...

Regular time..12am = midnight
Military time...12am = 0000

regular time..12pm = noon
military time..12pm = 1200

So I guess to make it easy..
just say 12 o'clock at night...
and 12 o'clock in the afternoon...

tg


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## danzomicrobo

I think that midnight is neither AM or PM, but how do I argue with my digital alarm clock, which thinks that midnight is 12:00AM?


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## lourai*87

I think the word says it all 

midday - middle of day (12:00 PM is always the middle of the day)


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## lsp

It's easy to remember if you add one second or one minute... 

12:01 - the minute after midnight - is AM, everyone agrees on this, right? 
12:01 - the minute after noon is PM, right?

AM starts with 12:00 midnight (12:00:00) 
AM continues (with 12:00:01 AM through 12:00:59 AM until) 12:01 AM, 12:02 AM, etc.


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## Laura_1414

It is midnight because 12pm is noon
From Laura_1414


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## charmedboi82

timpeac said:
			
		

> Thanks for clearing that up, but it might be good if you could add your evidence.



What evidence is needed?  It occurs in the middle of the night, right?  There ya go!


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## josama

Sorry for the belated post.


I live in Colombia, and my mother and teachers taught me that, as AM comes from latin: ante meridien and so does PM (post meridiem) the only and only logical way of expressing 'noon' is M (meridiem) because it is not before, nor after the noon, but at noon!!!

the expression for midnight is MN (in Spanish, media noche, so it also seems international)

But, in fact, 12AM doesn't exist at all. One millisecond after the clock hits 12MN, it is 0:00AM

If this is causing so much trouble, it is time to start using the other systems around. The USA, as usual, is behind the rest of the world, where the 24 hour time is increasingly widespread. The same has happened with the SI of units.


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## modgirl

I think a 24-hour clock is so much easier.  If you tell me to meet you at the train station and that your train arrives at 8:00, is that morning or evening?  Certainly, we usually try to clarify, but just saying 0800h or 2000h is so much easier.


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## Merlin

modgirl said:
			
		

> I think a 24-hour clock is so much easier. If you tell me to meet you at the train station and that your train arrives at 8:00, is that morning or evening? Certainly, we usually try to clarify, but just saying 0800h or 2000h is so much easier.


Normally here in the Philippines, we normally call 12am as 12 midnight. The 24-hour clock is normally used here as military time.


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## detiquilin

I have always 'known' that 12 am is midnight. And for me it makes sense. Thnk about it. Before there is a 1 o'clock there has to be a 12 o'clock right? Well if it is 1 o'clock _am in the morning _then wouldn't the 12 o'clock be _am, also in the morning? _Same for pm. Anyway, hope this helps.


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## panjandrum

I have tried really hard to resist this old thread, but the restraint is too much.

Before there is a 1 o'clock there has to be a 12 o'clock, right?
Before there is a 12 o'clock there has to be an 11 o'clock, right?

Which of those makes most sense?

If people insist on using 12am and 12pm it is usage and convention, not logic, that decides which is midnight and which is noon.

Ah, that's better.  I can rest easy now.


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## meili

I agree, Panj.
I say that 12AM is midnight, BTW.


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## daviesri

josama said:
			
		

> The USA, as usual, is behind the rest of the world, where the 24 hour time is increasingly widespread. The same has happened with the SI of units.


 
 I do not think we are behind the  rest of the world, I feel that we are just independent thinkers that choose when and when not to follow.  Why fix it if it ain't broke.  Personally though, I like the 24 hour clock and the date method (dd/mm/yy vs mm/dd/yy) but I cannot deal with the metric system.  True, it is simpler, but it would throw away years of schooling that tauqht me how many pints to a quart, quarts to a gallon, feet to a yard and to a mile and so on.


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## josama

daviesri said:
			
		

> I do not think we are behind the rest of the world, I feel that we are just independent thinkers that choose when and when not to follow.


 
If Americans want to keep a system which is more difficult, it's OK for me. I just wanted to make it easier for you guys. BTW, The USA *wants to go metric, *and is making efforts in that direction -not enough, though.

Do you know how much money does USA lose because of "being different" from the rest of th world?

Here are some clues:

Fiction: Metrication costs money. Fact: Not metricating costs more

NASA IG recommends metric reforms


CNN - Metric mishap caused loss of NASA orbiter - September 30, 1999

Furthermore, it not only about metric, is the whole SI.



> Why fix it if it ain't broke. Personally though, I like the 24 hour clock and the date method (dd/mm/yy vs mm/dd/yy) but I cannot deal with the metric system. True, it is simpler, but it would throw away years of schooling that tauqht me how many pints to a quart, quarts to a gallon, feet to a yard and to a mile and so on.


 
Because the World doesn't revolve -or at least shouldn't revolve- around the US. It'll cost a lot to "throw away" years of schooling, but it is not costly to teach the kids nowadays how to use the SI.


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## lsp

32 posts for two opinions and that's only in this thread - which by the way is about time. I think the metric system debate is supposed to get its own (interminable) thread.


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## RazzRick

CAn someone help me please i got a question


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## mylam

Sure, start a new thread in the appropriate forum. You might want to read the rules first, though.


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## aceizace

Sorry for replying to such an old post, I found this while searching for what the "o'" is short for in "o'clock" and decided I had to post my views.

I learned, from reading digital watches, to call midday PM and midnight AM, although I agree that technically neither is correct, it is simply 12 midday or 12 midnight. However, there is still a logical reason for arguing it this way over the other way round:

Imagine an unbelievably small unit of time, let's say, the amount of time it takes for light to travel one billionth of a nanometre, and let's call this T because it's too long otherwise. Now I'm sure you'll all agree that at T past midday, the time is PM, but I'm also sure you'll agree that the clock will still display 12:00, because not even close to a minute has passed. 

No one can ever say "it's exactly noon...... now!" and be 100% acurate, and since everyone goes by their watch or clock, if it displays 12:00pm the time is definately past noon, simply because of the time it takes the electricity to light the LEDs that display "PM", so I think it's fair enough to say 12:00pm. 

If you want to be a purist, then 12AM doesn't exist, it is either 12 midday or 12 midnight, but to be even slightly practical, 12AM is midnight.

Once again, I'm sorry for posting in such an old thread, and also for making my reply so long.
-
Andrew


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## maxiogee

aceizace said:
			
		

> No one can ever say "it's exactly noon...... now!" and be 100% acurate,



In this case, no time announcement can be accurate, but we can say "It's around noon", or "It must be close to midnight". So we do need to have a name for these times.


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## boonognog

I've seen people write out 12NOON just to avoid discussion and confusion.


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## aceizace

maxiogee said:
			
		

> In this case, no time announcement can be accurate, but we can say "It's around noon", or "It must be close to midnight". So we do need to have a name for these times.


 
Yes definitely, I was just trying to point out that if anyone was trying to say that the time was midday there's a negligible chance that it is actually spot on.


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## maxiogee

aceizace said:
			
		

> Yes definitely, I was just trying to point out that if anyone was trying to say that the time was midday there's a negligible chance that it is actually spot on.



Maybe in England  

We're a bit more relaxed about time over here and a guy with a stammer and a faulty watch could announce it and still be accurate when he finished!  

So do I take it then that you don't eat a midday meal!


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## texasweed

I've heard that due to this ambiguity, no airplanes ever take off at 12:00 in the States. 
Not sure if it's true? Or if it applies to other Countries as well?


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## maxiogee

Sounds like an urban myth. Airlines all use the 24 hour clock - where would the ambiguity arise?

A quickish search finds this flight leaving on Wednesday

Flight:	CO 1833 (Continental Airlines)
Depart:	New York La Guardia Apt	21 Jun 	12:00
Arrive:	Houston George Bush Intercontinental Ap	21 Jun 14:52


And for departures tomorrow from Dublin Airport 

Frankfurt........Aer Lingus.....EI651........12:00
Bratislava.......Ryanair........FR4283.......12:00


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## texasweed

maxiogee said:
			
		

> Sounds like an urban myth. Airlines all use the 24 hour clock - where would the ambiguity arise?


The answer seems obvious to me. THEY use a 24-hour clock, but WE don't. Your flight is at 12 PM/AM meaning nothing, how would we know which it is? I once had a 11:59 AM flight and was told this. Myth or not, I can't say.


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## boonognog

I heard planes don't stick to any schedule just to avoid this ambiguity.


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## panjandrum

From experience, ferry departures will be at 00:05 or 23:55 rather than 00:00.

Some may consider this to be simply a matter of timing.  I am quite sure it is to avoid confusion.


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## se16teddy

12 am and 12 pm should not be used because they are ambiguous. Use 12 midnight and 12 noon instead. Especially as 'midnight' and 'noon' are beautiful and evocative and English words, unlike 'am' or 'pm'. 

If you wish to nit-pick about what they ought to mean, I would say that am (ante meridiem) means 'before midday', and pm (post meridiem) means 'after midday'. The first 12.00 before midday is midnight, and the first 12.00 after midday is midnight. Thus for 4th April, 12.00 am is the midnight between the 3rd and 4th, and 12.00 pm is the midnight between the 4th and 5th.


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## johncat

A group of teachers at my school are argueing as to the correct time term for 12 noon and 12 midnight.
Some say you should express 12 noon as 12 p.m. and some say it should be 12 a.m. the same situation occurs concerning Midnight.
I have posted this on Ajarn.com in Thailand, and as yet do not have a satisfactory answer, But Englishclub.com and Greenwich mean time say 12 noon and 12 midnight cannot be expressed as a.m or p.m. because 12 noon is neither a.m. or p.m. ( or it could be both ) the same applies to midnight. 
I am just looking for the correct answer to tell my students.


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## Dimcl

I think of 12:00 A.M. as midnight and 12:00 P.M. as noon.  This is, however, a perfect example of why we should switch to the 24-hour clock (1200 hours and 2400 hours).


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## Hockey13

Dimcl said:


> I think of 12:00 A.M. as midnight and 12:00 P.M. as noon. This is, however, a perfect example of why we should switch to the 24-hour clock (1200 hours and 2400 hours).


 
I think you will see most alarm clocks and such things refer to midnight as 12:00 A.M. and noon as 12:00 P.M. I suppose the idea is that 12:00:01 and even 12:00:00.000000001 is already past the midpoint of the clock. Midnight could go either way, but sticking by the midpoint thing that you have at noon, you should say 12:00 A.M.

It's all very complicated and by the time you've got it figured out, it's already 12:01 and you know what time it is anyway.

In other words, I agree with Dimcl.


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## Brioche

timpeac said:


> What time of day is 12AM. Is it midnight or midday?
> 
> I was talking with people at work about this, and not everyone agreed.
> 
> It suggests midnight to me, but I think that it is ambiguous.


 

I hate the expressions 12 pm and 12 am, when midday/noon and midnight are what is really meant.

However, I can understand how it came to be.

Imagine the early digital-display clocks. 
They did not have VFDs, LCDs or LEDs, they had flat plastic leaves attached to wheels.
As the wheels turned, a new leaf would flip down each minute: 00, 01, 02 ..... 58, 59

Similarly a leaf flipped down every hour: 1am, 2am, 3am, 4am ...

It would not have been practical to have a 12 noon leaf, to show for one minute, to be followed by a 12 pm leaf.

So digital clocks went 11am:59, 12pm:00, 12pm:01, and so on.

Thus 12pm was associated with 12 noon, and 12am with midnight.


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## jaxineau

do a search for english definition.

since PM, post meridiem, means between noon and midnight, that means that midnight must not be 12PM and AM, ante meridiem, is before noon then 12AM fits totally.

and noon should not really be 12PM because of this reason. however, the real noon only stays for that split second. 12:00:00 instantly becomes 12:00:01, so 12PM works.


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## Hockey13

jaxineau said:


> do a search for english definition.
> 
> since PM, post meridiem, means between noon and midnight, that means that midnight must not be 12PM and AM, ante meridiem, is before noon then 12AM fits totally.
> 
> and noon should not really be 12PM because of this reason. however, the real noon only stays for that split second. 12:00:00 instantly becomes 12:00:01, so 12PM works.


 
I thought post meridiem meant after noon and ante meridiem meant before noon. If ante meridiem means before noon, how could it be that post meridiem means between noon and midnight? I'm no Latin scholar, but...


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## lsp

Can we at WordReference really resolve a debate of this scale? 

Are noon and midnight 12 a.m. or 12 p.m.?, by the National Institute of Standards and Technology.


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## JamesM

Hockey13 said:


> I thought post meridiem meant after noon and ante meridiem meant before noon. If ante meridiem means before noon, how could it be that post meridiem means between noon and midnight? I'm no Latin scholar, but...


 
I've always thought it was meant to distinguish between the two times each day that the hands of the clock are in an identical position.  If the big hand is pointing to twelve and the little hand is pointing to nine, then it's easy to imagine that "(the) 9 before noon" and "(the) 9 after noon" are simple ways to distinguish between the two.

As for "midnight", I'm not sure if you're wondering if it literally means before midnight, but it would make sense that it would refer to all the hours of the same calendar day, which ends at midnight (or does it?  Another one of those questions that arise when talking about midnight.)


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