Equinox

in astronomy, either one of the two points at which the sun, in its annual apparent course among the stars, cro es the equator; so called because the days and nights are nearly equal when the sun is at these points. The vernal equinox occurs about March 20. When but one equinox is referred to, vernal equinox is meant. The autumnal equinox occurs about Sept. 23. It takes the sun seven or eight days longer to go from vernal to autumnal equinox than from autumnal to vernal. The term equinox is often used to denote the time or epoch at which the sun is at the equinee point, as well as the point itself.