(2) The phenomenon called “Equinox” is due to the revolution of the Earth on its inclined axis. An equinox is when the sun passes directly over the equator. Two days in a year when day and night are equal throughout the world are equinoxes. The word equinox comes from two Latin words meaning "equal" and "night". The vernal equinox occurs on March 21 and it is also called the spring equinox in the northern hemisphere and the autumnal equinox occurs on September 23.