A solstice is an astronomical event that occurs twice each year when the Sun is at its greatest distance from the equator. The solstices, which occur in June and December, mark the longest and shortest days of the year. During the June solstice, the Sun is at its highest point in the sky and the days are longest. During the December solstice, the Sun is at its lowest point and the days are shortest.
An equinox is an astronomical event that occurs twice each year when the Sun is directly overhead at the equator. The equinoxes, which occur in March and September, mark the transition from winter to spring and summer to autumn. At the equinox, the length of day and night is nearly equal. After the equinox, the days begin to grow longer until the June solstice and then shorter until the December solstice.