Equinoxes

Equinoxes occur twice a year when the Earth's tilt is such that the Sun is directly over the equator, resulting in nearly equal day and night lengths worldwide. This happens around March 21 (vernal equinox) and September 23 (autumnal equinox). They mark the start of spring and fall respectively in many regions. The equinox occurs because Earth’s orbit around the Sun causes the tilt of its rotational axis to align in a way that the Sun appears directly overhead at the equator, creating a balance of daylight and darkness.