March Equinox

One of two days during a year when the declination of the Sun is at the equator. The March equinox denotes the first day of spring in the Northern Hemisphere. In the Southern Hemisphere, this date marks the first day of fall. During the March equinox, all locations on the Earth (except the poles) experience equal (12 hour) day and night. The March equinox occurs on either March 20 or 21.