Noontime

[Ed Ancona]

What is the correct suffix for 12 noon. AM or PM

[Ed Ancona]

As the sun rises in the sky in the morning it approaches the meridian. The meridian is the imaginary line from the north pole to the south pole going through the highest point in the sky. In the morning, the sun is before the meridian (Ante Meridiem in Latin), and in the afternoon is after the meridian. (Post Meridiem in Latin.) Thus, morning hours are suffixed by A.M. and afternoon hours by P.M. The correct designation for noon, therefore, is 12:00M. Midnight would be either 12:00 A.M. or 12:00 P.M., depending on which way you are facing. Of course with a 24 hour clock there is no confusion. An old related joke about imaginary lines-- When the young schoolboy was asked to define the equator, he replied that it was a menagerie lion running around the center of the earth.

[joebananas]

According to The Oxford Guide to Style noon is p.m. It's only exactly "noon" for a second of course and anything after noon is p.m. but if you ever see 12:00 p.m. you should consider it to be noon as opposed to midnight.

[Ed Ancona]

I think that the definition for noon in the Oxford guide for style was certainly not written by an astronomer. At noon the sun is ON the meridian. Not before: AM, or after: PM. If one needs to have a legal difinition for some posting, such as "No parking before 12 PM," perhaps the court would refer to the Oxford. It seems to me, however, to be a potentially confusing situation. 12M leaves no doubt, except that not everybody knows much about astronomy.

[Ed Ancona]

Further to this issue -- there is a web site < target=_blank>http://greenwichmeantime.com/info/noon.htm> which notes that "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) To avoid confusion timetables, when scheduling around midnight, prefer to use either 23:59 or 00:01 to avoid confusion as to which day is being referred to." I don't know if the Oxford folk want to argue with the Greenwich folk, but I stand by my contention that noon can be correctly defined as 12:00M,and, contrary to the Greenwich article, 12:00 PM or 12:00 AM do have meaning in that they indicate 12 hours after or 12 hours before noon. Of course if we just say "noon" then there is no problem.

[Waterwolf]

So you've answered your own question..?