Noon (or midday) is 12 o'clock in the daytime, as opposed to midnight. It is written as 12 noon, 12 p.m. (for post meridiem) or 12 pm. Solar noon is the time when the Sun appears to contact the local celestial meridian. This is when the Sun apparently reaches its highest point in the sky, at 12 noon apparent solar time and can be observed using a sundial. The local or clock time of solar noon depends on the longitude and date.