The September equinox falls on Sunday, September 22, at 20:44 (8:44 p.m.) Universal Time. At this special moment, the sun will be at zenith – straight overhead – at the Earth’s equator. Although the equinox happens at the same instant for everyone worldwide, the clock time for the equinox varies by time zone. In the U.S., the equinox will come on September 22, at 4:44 p.m. EDT, 3:44 p.m. CDT, 2:44 p.m. MDT or 1:44 a.m. PDT.
At the instant of the September equinox, the midday sun will be shining straight overhead at the equator. As the September equinox sun crosses the equator, going from north to south, it’ll signal the beginning of autumn in the Northern Hemisphere and spring in the Southern Hemisphere.
Day and night sides of earth at instant of September 2013 equinox
On the day of the equinox, the sun rises due east and sets due west all over the world, with everyone worldwide receiving the same amount of day and night. By October, however, that’ll change dramatically. By then, the sun will rise noticeably south of due east and will set noticeably south of due west. That’ll mean shorter days and longer nights for the Northern Hemisphere, yet longer days and shorter nights in the Southern Hemisphere.
After the equinox, the sun and the migrating birds will continue to travel southward to the warmer climes. Watch today, on September 22, as the sun rises due east and sets due west on the great day of the equinox.