Noon

Solar noon is the time when the Sun appears to contact the local celestial meridian.

[1] The word noon is derived from Latin nona hora, the ninth canonical hour of the day, in reference to the Western Christian liturgical term Nones (liturgy), (number nine), one of the seven fixed prayer times in traditional Christian denominations.

The elapsed time from the local solar noon of one day to the next is exactly 24 hours on only four instances in any given year.

This occurs when the effects of Earth's obliquity of ecliptic and its orbital speed around the Sun offset each other.

This event time and location also varies due to Earth's orbit being gravitationally perturbed by the planets.

The equation of time shows that the reading of a clock at solar noon will be higher or lower than 12:00 by as much as 16 minutes.