The first day of fall in 2025, also known as the autumnal equinox, occurs on Monday, September 22, 2025, at 2:19 p.m. Eastern Daylight Time (EDT), which corresponds to 18:19 UTC. This moment marks the sun crossing the celestial equator, signaling the start of astronomical fall in the Northern Hemisphere. On this day, day and night are nearly equal in length.