Who, What, Why: What is an equinox?

The September equinox marks a moment of balance — when day and night are equal (nearly) across the globe. In 2025, the equinox occurs on September 22 at 18:19 UTC (1:19 p.m. CDT). That's when the sun shines directly over Earth’s equator. This equinox brings summer to Earth's Southern Hemisphere and winter to the Northern Hemisphere. Join EarthSky's Deborah Byrd as she explores the science behind the equinox, how Earth’s tilt shapes our seasons, and the signs of seasonal change all around us. Pro