When is the vernal equinox?

The vernal equinox is one of the 24 solar terms. Every year on March 20th or at 2 1 day of Gregorian calendar, the sun starts when it reaches 0 degrees of the yellow meridian (vernal equinox). It is a day with an average length of day and night, which is exactly half of the ninety days in spring, so it is called "vernal equinox". The autumnal equinox is the sixteenth solar term in the twenty-four solar terms of the lunar calendar, usually on September 23rd or 24th every year.

The autumnal equinox means "half" China's ancient book "Spring and Autumn Dew, Yin and Yang in and out" said: "The autumn equinox is half cloudy, so it is cold and hot."