Overview
- The equinox is the instant the Sun crosses the celestial equator, signaling spring in the Northern Hemisphere and autumn in the Southern Hemisphere.
- Because the tropical year lasts about 365.2422 days, leap-year rules shift the equinox across 19–21 March; it has fallen on 20 March since 2008, with 21 March projected for 2102 and 19 March for 2044.
- Day and night are only nearly equal at the equinox, as atmospheric refraction and sunrise/sunset conventions make exact “equiluce” vary by latitude.
- The moment anchors cultural traditions, including Nowruz in Iran and the ecclesiastical calculation that sets the date of Easter.
- Italy returns to daylight saving time overnight on 29 March 2026, a few days after the equinox.