The first day of Spring!
There are two equinoxes every year, one in March and one in September. The March equinox is the moment the Sun crosses the celestial equator – an imaginary line in the sky above Earth’s equator, from south to north. This happens on March 19, 20, or 21 every year.
Why Is It Called “Equinox?”
On the days of the equinoxes, the Earth’s axis is perpendicular to the Sun’s rays, meaning that all regions on Earth receive about the same number of hours of sunlight. In other words, night and day are, in principle, the same length all over the world.
This is the reason it’s called an “equinox,” derived from Latin, meaning “equal night.”