The first day of fall in 2023 is on Saturday, September 23, in the Northern Hemisphere. This day is also known as the autumnal equinox, which is the day of the year when day and night are approximately equal in length all over the world. During this time, the Earths axis is tilted neither toward nor away from the sun, causing all latitudes to experience a basically equal amount of daylight and darkness. The first day of fall can change, but the window of possible dates is quite small. Most years, you can expect it to occur on September 22 or 23. Every now and then, it could happen on September 21 or 24, but the last time we had a September 21 fall equinox was over a thousand years ago! And dont expect another September 24 date until 2303.