The September Autumn Equinox occurs around September 22nd or 23rd each year.
It marks the beginning of autumn in the Northern Hemisphere.
On this day, day and night are approximately equal in duration.
The equinox results from Earth's tilt causing the Sun to cross the celestial equator.
In the Southern Hemisphere, it's the Spring Equinox and marks the start of spring.
The word "equinox" comes from Latin, meaning "equal night."
Many cultures celebrate the equinox with festivals and rituals.
It's a critical event for astronomers and is used to define the start of various astronomical seasons.