Wednesday's autumnal equinox heralds the arrival of a darker and colder season.
Most of the Earth will experience about 12 hours of daylight and 12 hours of darkness during the fall equinox.
Summer often seems to last deep into September these days. However, the autumnal equinox — which arrives Wednesday at 3:21 p.m. Eastern time — is a reminder from Mother Nature that fall is finally on our doorstep. We are now seeing just over 12 hours of daylight, having reached the halfway point between our longest and shortest days of the year.
The autumnal (or fall) equinox, which usually falls on Sept. 22 or 23, is technically not a day-long astronomical event. It’s a brief moment in time when the sun appears directly over the Earth’s equator before crossing into the Southern Hemisphere. Like the spring equinox in March, the fall equinox is one of only two days each year when most of the Earth experiences about 12 hours of daylight and 12 hours of darkness. Day and night are nearly equal because we are at a point in our orbit when neither hemisphere is tilted away from or toward the sun. . .
Friday will be our last sunset in the 7 o’clock hour this year. Beginning Sunday (Sept. 26), the length of day dips to 11 hours and 59 minutes. Not until March 17, 2022, will the sun again spend more than 12 hours above the horizon.
https://www.washingtonpost.com/weather/2021/09/21/autumn-fall-equinox-dc-2021/?