What happens in the northern hemisphere on September 23rd?

On September 23rd, the Northern Hemisphere experiences the autumnal equinox, marking the official start of fall. During this event, day and night are approximately equal in length as the sun crosses the celestial equator. This phenomenon occurs because the Earth's axis is tilted neither toward nor away from the sun, resulting in balanced daylight and darkness across the globe. Following the equinox, days will gradually become shorter as winter approaches.