Equinox is a spring club.

1. Before and after the vernal equinox is the Spring Society, which is also the biggest sacrificial activity at the vernal equinox. Social Day is a festival for ancient farmers to worship the land god. Before the Han dynasty, there were only spring clubs, and after the Han dynasty, there were autumn clubs. In the Zhou Dynasty, the Spring Festival society was held on the first day after the vernal equinox, which was the most important ritual activity of the emperor. Because the "e" in the five elements belongs to the earth, after the Han Dynasty, the day after the vernal equinox was changed to the day of offering sacrifices to the Spring Society. Later, since the Song Dynasty, Social Day was designated as the fifth day after beginning of spring and beginning of autumn.

2. The vernal equinox is the fourth of the 24 solar terms and an important season for farming. The sun shines directly on the equator of the earth, and day and night are almost equal. In ancient times, it was spring from beginning of spring to long summer, and the vernal equinox was in the middle of three months in spring. The sun reaches the longitude of the Yellow River at 0 degrees, in March every year in Gregorian calendar 19~22. "The vernal equinox, Yin and Yang. So it's hot and cold day and night. " According to the lunar calendar, "it refers to the vernal equinox, which is about Sunday. The northern and southern hemispheres are equally divided day and night, which is also half of spring, so it is called the vernal equinox." From this day on, the direct position of the sun gradually moved northward, and the length of day and night in the northern and southern hemispheres also changed. The northern hemisphere has long days and short nights, but the southern hemisphere is just the opposite.

3. As soon as the spring equinox arrives, the rainfall increases obviously, and the national average ground temperature has stabilized at 10 degrees, which is the spring temperature defined by climatology. However, after the spring equinox and solar terms, the climate is mild, the rain is abundant and the sun is shining. Winter crops in most parts of China enter the spring growth stage, which is also the sowing time of early rice.

There are three stages in the vernal equinox: "Wait for the birds to arrive, wait for the thunder, and wait for the electricity to rise". Sending pictures of spring cows is also one of the customs of the vernal equinox. In addition, the vernal equinox customs such as offering sacrifices to hundreds of birds and sticking birds' mouths also carry people's expectations for farming time.