Autumnal Equinox 2025 Marks the Start of Fall on September 22

The autumnal equinox in the Northern Hemisphere in 2025 occurs on September 22 at 2:19 p.m. EDT, marking the start of fall, with the sun crossing the equator. The article explains the complexities of equinoxes, including atmospheric refraction and twilight effects, which cause day and night not to be exactly equal. It also clarifies misconceptions about polar daylight and darkness, highlighting that twilight extends the period of light or darkness beyond the simple day/night division.