No, no, no. The military (which uses internation standard time notation) has no concept of AM or PM. Look at 1200 hours, which is noon. That can be read “one two zero zero hours”, “one thousand two hundred hours”, or “twelve hundred hours”. “Twelve hundred hours” is shorter to say, and for that reason is used.
To continue the military time hijack, how do you pronounce 0000? Is it “zero hundred hours”?
See, butler1850, you’re just being ornery. If I want somebody to meet me at a particular time, I’m not going to get pedantic about “common usage” or what’s “scientifically correct.” I’m going to provide the least ambiguous information I can.
Saying 12:00pm may be acceptable common convention for “noon,” but a lot of people don’t know or can’t remember that. The word “noon” is so clear and unambiguous that there’s no possibility of error. Why not use it?
As Foghorn Leghorn would say: It’s a joke, son, you missed it! I keep pitchin’ ‘em, and you keep missin’ em! You’re built too low, the fast ones go over your head! Pay attention when I’m talkin’ to you, son. Now what’s going on in that little round head?
When I was in the Army, it was refered to as either “zero hundred hours,” or simply, “zero hour.”
I wonder who’s being ornery. I have never in my real life interacted with a person with whom I had to discuss scheduling of some kind who expressed confusion concerning the meaning of “12 p.m.”
This has been my experience with military folks. Note that “hundred” often is used only to denote “on the hour”. Thus I’d expect if a military person wanted to meet with me at 9:00 PM, she’d say “meet me at 21 hundred”. However, if the meeting time was 9:15 PM, this likely would be said “meet me at twenty one fifteen.” Because the context obviously would be a time of day, the “hundred” is superfluous. A civilian parallel would be “meet me at 9 o’clock sharp tonight.”
Note also that it written form the colon is omitted by standard. Thus if this woman were to state the time of the meeting to me in e-mail, “meet me at 2100 today” would be the expected form. Also, before 10:00 AM time is usually expressed writing with a lead zero. Thus if this military woman wanted me to meet with her at 9:00 AM, “meet me at 0900 tomorrow” would be expected more than “meet me at 900 tomorrow.” The 4 digit notation is used to make it obvious that the number is a time of day.
The military isn’t the only entity that uses 24 hour notation. In many parts of the world it is standard, particularly in print form. I wouldn’t find a French language TV schedule listing programs after noon as starting at 1300, etc. odd.
In oral conversation “noon” is also shorter than “twelve hundred hours”. Hence why in the military “zero hour” is often used as mentioned before instead of “zero hundred hours.” 2 less syllables to utter.
In Italy everyone uses the 24-hour clock. They don’t even need to say the equivalent of “o’clock,” they just say the number preceded by the feminine plural article. So to say “It’s eleven o’clock” in Italy, you say Sono le undici, literally ‘they are the eleven’. To say 'It’s twelve noon," they say Sono le dodici (they are the twelve), and to say “It’s one o’clock PM”, they just say Sono le tredici (they are the thirteen). No AM, no PM, no military, no o’clock. Just the plain numbers up to 23 is enough for Italians.
I write 13:00 (and sometimes say, thirteen o’clock). But that’s just me.
It’s when I hit 25:00 that you should start worrying…
I just know I’m gonna ask something terribly stupid, but, I will, anyway. What do Italians say for midnight?
(Was this covered in a previous post?)
InvisibleWombat you’re right in my book. Using noon and midnight leave no room for error. There are a lot of people in the world who get 12pm and 12am screwed up.
I deal with a lot of older folks in scheduling a running 24-hour devotion. If I told one of them to go to the Chapel at 1200 or 2400 hours, I chuckle just at the thought of their reactions.
But if I say noon or midnight, they know exactly what times those are.
No, ****, I’m not being ornery. I have dealt with quite a few people who asked me to clarify what was meant by 12 p.m.–I stopped using it years ago because it was ambiguous. As others mentioned in the thread, the term “pm” is meaningless when applied to midnight or noon anyway, so by saying “noon” instead I’m being clearer and more concise.
Mezzanotte.
You reminded me of something funny. You know how the South of France is called le Midi and Southern Italy is called il Mezzogiorno? These names mean ‘midday’. Because at midday the sun is in the south.
So the Economist once published a satirical map of Great Britain in which everything had been renamed Italian-style. Scotland was labeled “Mezzanotte.” 
I agree with others that in everyday conversation one should use “noon” and “midnight”, and that’s easy enough to do. The problem is with forms and data entry where the only option is 12:00 AM or PM. In my experience most people get around the ambiguity by entering 12:01 AM or PM.
acsenray, I suspect the only reason that you have never encountered any ambiguity regarding 12PM is because of the context. Even if you said “Let’s get to gether for lunch at 12AM” everyone would know exactly what you meant. Most people probably wouldn’t even notice the mistake.