An equinox is the moment in which the plane of Earth‘s equator passes through the center of the Sun‘s disk,[2]which occurs twice each year, around 20 March and 23 September.
On an equinox, day and night are of approximately equal duration all over the planet. They are not exactly equal, however, due to the angular size of the sun and atmospheric refraction. The word is derived from the Latin aequinoctium, from aequus (equal) and nox (genitive noctis) (night).
