The Noon reference article from the English Wikipedia on 24-Apr-2004
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Noon

Noon is 12 o'clock (12:00) P.M., or when the Sun appears the highest in the sky, compared to its positions the rest of the day. It occurs when the Sun is transitting the celestial meridian. This is also the origin of the terms A.M. (Ante Meridiem) and P.M. (Post Meridiem).

See also: 12-hour clock