Equinoxes are the moments in time when the Sun is directly over the Earth’s equator, and day and night are of equal length. They occur twice a year: around March 20 – 21 (the Vernal or Spring Equinox) and around September 22 – 23 (the Autumnal or Fall Equinox). During equinoxes, the length of day and night is nearly equal, but not exactly equal.