An equinox occurs twice a year, when the tilt of the Earth's axis is inclined neither away from nor towards the Sun

2. An equinox occurs twice a year, when the tilt of the Earth's axis is inclined neither away from nor towards the Sun. During this time the center of the Sun is in exactly the same plane as the Earth's equator. During an equinox the length of day/night is nearly equal.
3. A solstice is an astronomical event that happens twice each year when the Sun's apparent position in the sky reaches its northernmost or southernmost extremes. During this time the length of day (for summer solstice) and night (for winter solstice) is at its longest.