Equinox During Earth's annual journey around the sun, we observe the sun's apparent position among the stars. This path is called the ecliptic. When the sun crosses the celestial equator (the projection of the Earth's equator onto the celestial sphere) and enters the southern hemisphere, it is the time for the autumnal equinox, which occurs this year on Sept. 22. The autumnal equinox begins the first day of fall in the northern hemisphere and the first day of spring in the southern hemisphere. "Equinox" is a Latin word meaning "equal night," signifying there is an equal amount of daylight and night time on this day. During the autumnal equinox the sun will rise directly east and set directly west. The next time the sun will cross the ecliptic will be in March for the vernal equinox, the first day of spring in the northern hemisphere and the first day of fall in the southern hemisphere. It will cross into the northern celestial hemisphere.