when is fall equinox

The fall equinox in 2025 will occur on Monday, September 22. The precise moment will be at 2:19 p.m. Eastern Daylight Time (EDT), which corresponds to 19:20 British Summer Time (BST) and 18:20 Greenwich Mean Time (GMT). This event marks the official start of autumn in the Northern Hemisphere and is characterized by the Sun crossing the celestial equator, resulting in nearly equal lengths of day and night across the globe.