I know what most people think, but all my research indicates that Noon is actually 12AM and not 12PM (although this is common practice). Can anyone give meaningful and supported evidence to the contrary?
Noon is neither AM or PM. Noon (and midnight) are the instant between those two. Consider one millisecond after noon as PM, and one millisecond before noon as AM - but noon itself stands proudly alone.
It’s really neither. AM means “ante meridiem” meaning, basically, “before noon”. PM, “post meridiem” meaning “after noon”.
So is noon before noon or after noon? Neither, it’s just noon. Same with midnight since it’s just on the other side of the day from noon.
A sound argument to be sure, but there must be a convention written down somewhere by the lords of space and time.
Yeah, there is a convention, and that convention is to refer to them as 12 noon and 12 midnight.
I’ve seen it written 12 AM/PM many times, sometimes AM = midnight, sometimes AM = noon (most commonly the former), but it really is ambiguous to do that. I can’t make a convincing argument for one over the other because it’s really not either.
Midnight is 12AM, noon is 12PM.
BYW; Military time sucks. 
Peace,
mangeorge
No, one minute after noon is 12:01 PM, but noon is just noon.
What? That doesn’t make sense.
1 am is right after midnight. Zip down to 11 am, which is right before noon. Since 12 comes directly after 11, it is still am. We’ve started over, and now we’re at 1 pm. Zip up to 11, it’s still pm. 12 is STILL after 11, therefore, midnight is 12pm.
–Tim
I’m with the 12 noon and 12 midnight people, as the other versions are irritating or meaningless or both. BUT, I just looked in my dictionary, and I wish I had not. Apparently, “noon” is ultimately from Latin “nona” (hora) referring to the ninth hour from sunrise. (Huh! say I, looking out of the window.) However, even if there is a case against the word “noon” itself, we can still refer to 12 midday and 12 midnight.
One millisecond after midnight is 12:00:00.000001 AM. So if the 12 o’clocks need to be AM or PM, midnight would be AM.
That’s a few too many zeroes for a milisecond, but the premise is correct. Convention is to call midnight 12:00 AM and noon 12:00 PM. I’ve never seen it any other way. While true that the exact instant of noon and midnight are neither, writing it any other way would be incorrect with respect to societal and scientific standards.
The least confusing is, of course, to just say “noon” or “midnight.”
I use 24 hour time. Noon is 1200 and midnight is 0000. This problem never once comes up. So ha! 
Cecil addressed this question in this column.
I’m not satisfied with noon being neither AM or PM. Further, I think the fact that noon is typically written as 12:00PM isn’t sufficient evidence to show that that is correct. My one written source (which settled the argument in my mind) was from a Webster’s Dictionary under the definition for ante meridian wherein a footnote clearly stated, “Although noon is 12:00am and midnight is 12:00pm, noon and midnight should be used to avoid confusion.” Leading me to believe that while most of you are correct regarding the use of noon and midnight in lieu of the AM/PM appendages, a correct use is out there.
Chronos?
My vote is for noon as PM, mainly because I’ve always done it that way, but also because 12:05, etc, are clearly PM - post meridian, and it seems strange that 12:01-12:59 would all be PM, but 12:00 would be AM. Why single that poor minute out?
A computer program asked to display a time as HH:MM XX (where HH represents the hours, MM represents the minutes and XX represents “AM” or “PM”) will display noon as 12:00 PM and midnight as 12:00 AM (check this in Excel, for instance). Likewise, if you were asked to enter a time in that format, you would use those same values to indicate noon or midnight. We are indeed talking about precisely noon and precisely midnight, to the limit of resolution of the particular program.
Cecil is obviously correct that by human standards both noon and midnight are neither Post- nor Ante-Meridian. However stupid computers, lazy programmers, and carefully formatted reports cannot handle “noon” and “midnight” as legitimate display or input values. Therefore, for computers at least, the 12:00 PM=noon/12:00 AM=midnight convention has become the invariable standard.
In the Associated Press style guide, you are supposed to use “Noon” and “Midnight”. I believe that’s the New York Times style as well.
As far as I’m concerned 12 is a neutral marker. When both hands point straight up you’re on a cusp.
Let’s give the nod to Bob. We have two good words…“Noon” and “Midnight.” Use those two words and you have communicated so well that there is no room for debate.
I have always used 12 AM = midnight & 12 PM = noon.
Now, thanks to the SDMB, I am healed.
From now on, it will be 12 midnight & 12 noon for me.
Amen!
0000 and 1200…easy!