March Equinox – Equal Day and Night, Nearly
There are two equinoxes every year – in March and September – when the Sun shines directly on the equator and the length of night and day are nearly equal.
The Sun Crosses the Equator
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.