Each year, two equinoxes happen, one in March and another one in September.Equinoxes happen when the Sun shines directly on the equator. The word ‘equinox’ is derived from Latin, meaning ‘equal night’. Therefore, during equinoxes, the length of day is almost equal to the length of night.
The March equinox marks the moment the Sun crosses the equator. The equator is the imaginary line on the spheroid’s (Earth) surface, dividing it into northern and southern hemispheres at equal distance. The March equinox normally happens on March 19, 20 or 21 each year.
The March equinox is the spring equinox in the Northern Hemisphere and the fall equinox in the Southern Hemisphere. It is the first equinox of the year as the second one happens in September. Scientists and astronomers in the Northern Hemisphere use the March equinox as the start of spring that ends on June solstice, when summer begins. However, meteorologists in the Northern Hemisphere start their spring three weeks before the March equinox, i.e. on March 1 and ends on May 31.
The equinox occurs at a specific point in time when the Sun crosses the equator but many cultures around the world celebrate the whole day as the March equinox