Autumnal equinox this Thursday, Sept. 22 at 10:21 a.m. Eastern Daylight Time

The exact minute of the autumnal equinox this year is 10:21 a.m. Eastern Daylight Time on Sept. 22. This marks the moment that the sun crosses the celestial equator from north to south as seen from Earth, ushering in the beginning of fall in the Northern Hemisphere. On the day of the equinox, an observer located on Earth’s equator will see the sun pass directly overhead at local noon, and it marks the beginning of six months of daylight at the South Pole and six months of nighttime at the North Pole. On any day other than the equinox, either the Northern or Southern Hemisphere is tilted towards the sun.

For observers, except those at the North and South poles, the sun on the equinox, from the Latin equi, “equal” and nox, “night,” rises due east and sets due west and stays up for 12 hours and down for 12 hours.