PM or AM

The abbreviations AM and PM stand for Ante Meridiem and Post Meridiem, respectively. The terms ante and post mean before and after. The term meridiem refers to when the sun is at the middle of its arc across the sky.

I just noticed many people are confused between the use of PM and AM for 12 noon. Many tend to use 12 am when refers it to 12 noon. Too bad, our prime media also using 12am when refer to the 12 noon. 

So? Is 12 noon 12 AM or 12 PM?

Some people think that it is neither 12AM nor 12PM. Those are improper terms.  I have googled and found this from The Grammarphobia Blog, and it well explained:

Q: 

The parking signs in my town refer to noon as 12 PM. Since “PM” stands for “post meridiem” (“after noon” in Latin), can 12 PM be used for noon itself?

A: 

The simple answer is yes, but I’d advise against doing it. Traditionally, the term “12 PM” is used for noon in countries like the US with a 12-hour clock.

For those who argue that noon and midnight are neither AM nor PM, I can only cite the American Heritage Dictionary of the English Language, which has the following Usage Note with the entry on PM:

“By definition, 12 a.m. denotes midnight and 12 p.m. denotes noon, but there is sufficient confusion over the meaning of a.m. and p.m. when the hour is 12 to make it advisable to use 12 noon and 12 midnight where clarity is required.”

I agree that “12 AM” and “12 PM” are confusing and should be avoided, but I would argue that “12 noon” and “12 midnight” are redundant. Why not simply say “noon” and “midnight”?

You may be interested in knowing that “meridiem” actually means midday in Latin, and that the terms “noon” and “midday” have not always been synonymous in English.

As the Oxford English Dictionary points out, the word “noon,” dating back to the year 900, originally meant “The ninth hour of the day, reckoned from sunrise according to the Roman method, or about three o’clock in the afternoon.” By the 14th century, according to the OED, the word “noon” had come to mean 12 o’clock.

Although dictionaries usually define “midday” as middle of the day or noon, it’s often used more loosely than the word “noon.” The entry for “noon” on Wikipedia, for example, describes midday as “the period of early afternoon, beginning at noon and lasting until mid-afternoon.”

And my Scottish friend also 'smiling' at us just now, when one of my team members mentioned 12am when she refers to 12 noon. So, hey...12PM means for 12 noon. Noted with rolling eyes!