The Sky Tonight Update: March 20, March Equinox
This March 20, the March equinox occurs at 10:29 UTC. The Sun will shine directly on the equator and there will be nearly equal amounts of day and night throughout the world. This is also the first day of spring (vernal equinox) in the Northern Hemisphere and the first day of fall (autumnal equinox) in the Southern Hemisphere.
The March equinox marks the moment the Sun crosses the celestial equator – the imaginary line in the sky above the Earth’s equator – from south to north. This happens on March 19, 20, or 21 every year.
Why is it called an Equinox?
On the equinox, night and day are nearly the same length–12 hours–all over the world. This is the reason it’s called an “equinox”, derived from Latin, meaning “equal night.” However, in reality, equinoxes don’t have exactly 12 hours of daylight.