Explications :
Noon, or noon solar (or noon pile) is the time when the sun is closest to the zenith (culmination), halfway between dawn and dusk. This is the time opposite to the solar midnight, when it is closest to the nadir.
It is at this time that the shadow of an object is the shortest: it indicates precisely the north (in the northern hemisphere) or the south (in the southern hemisphere), outside the equatorial zones between the two tropics.
Noon and 12 o'clock do not coincide in a given place for several reasons:
Sun time advances or delays throughout the year up to 16 minutes from a regular average hour (see Equation of time);
Clock time is a civil time that is in effect throughout a country or territory through the time zone system, while the time of the Sun is local and depends on the longitude of the observer;
setting up daylight saving time to save energy.
It is therefore an abuse of language when a person declares "It is noon." at 12 o'clock.
