On the vernal equinox the sun is directly over the equator which happens on or about March 21
On the autumnal equinox the sun is directly over the equator which happens on or about September 22
On the equinoxes, the Sun is directly over the equator and the length of the days and nights are the same. (Actually, they aren't QUITE the same. Because of the way that the Earth's atmosphere...
Depends whether you are in northern or southern hemisphere.These days are when the sun passes over the Equator on its way to the other hemisphere's new season.Vernal is spring, Autumnal is autumn....