What is the vernal equinox solar term?

The vernal equinox, one of the 24 solar terms, is the fourth solar term in spring. The solar term of the vernal equinox begins on March 20th or 2 1 day of the Gregorian calendar every year, and the sun reaches 0 degrees of the yellow meridian (vernal equinox) and ends on April 4th (or 5th). On the vernal equinox, the sun shines directly on the equator, and the length of day and night is almost equal, which is exactly half of the ninetieth day of spring, so it is called "vernal equinox". The vernal equinox is the fourth of the 24 solar terms. In ancient times, it was also called "Japan-China", "Day and Night Minute" and "Mid-Spring Moon", and it was celebrated around March 21(20th to 22nd) every year.

According to the "Twenty-four solar terms": "In mid-February, it is divided into half, which is half of ninety days, so it is called minutes." Another "Spring and Autumn Annals" said: "The vernal equinox, Yin and Yang are also half-phase, so it is cold and summer day and night." There is a "Li Mingshi Yi" cloud: "The dividing line, the point where Huangchi intersects, the sun is here, and the day and night are equally divided." Therefore, the significance of the vernal equinox, first, refers to the equal division of day and night, each of which is 12 hours; Second, in ancient times, it was spring from beginning of spring to long summer, and the vernal equinox happened to be in the three months of spring, and spring was equally divided.