Noon

Noon (or noon time) is 12 o'clock in the daytime, as opposed to midnight. It is written as 12 p.m. (for post meridiem) or 12 pm. It is synonymous of midday, which is of different concept and points to the middle of the day-light period. Noon and midday may not be on the same time.The word noon is derived from Latin nona hora, the ninth hour of the day, and is related to the liturgical term none. The Roman and Western European medieval monastic day began at 6:00 a.m. (06:00) at the equinox by modern timekeeping, so the ninth hour started at what is now 3:00 p.m. (15:00) at the equinox. In English, the meaning of the word shifted to midday and the time gradually moved back to 12:00 local time (that is, not taking into account the modern invention of time zones). The change began in the 12th century and was fixed by the 14th century.Solar noon (informally high noon) is the moment when the Sun contacts the observer's meridian, reaching its highest position above the horizon on that day ('Sun transit time'). This is also the origin of the terms ante meridiem (a.m.) and post meridiem (p.m.), as noted below. The Sun is directly overhead at solar noon at the Equator on the equinoxes, at the Tropic of Cancer (latitude 23°26′12.3″ N) on the June solstice and at the Tropic of Capricorn (23°26′12.3″ S) on the December solstice. In the Northern Hemisphere, north of the Tropic of Cancer, the Sun is due south of the observer at solar noon; in the Southern Hemisphere, south of the Tropic of Capricorn, it is due north.In the US, noon is commonly indicated by 12 p.m., and midnight by 12 a.m. While some argue that such usage is 'improper' based on the Latin meaning (a.m. stands for ante meridiem and p.m. for post meridiem, meaning 'before midday' and 'after midday' respectively), digital clocks are unable to display anything else, and an arbitrary decision must be made.