The vernal equinox starts from March 20 to April 4. The vernal equinox, the annual Gregorian calendar on March 20 or 21, begins when the sun reaches 0 degrees Celsius. The average day and night of this day is just half of the 90th day of spring. It is called the "spring equinox". On the equinox day, the sun shines directly into the equator and stays up close to the equator. After that, the location of the direct sunlight gradually moves northwards and begins to grow. The vernal equinox is an important solar term. It not only has astronomical significance: it divides equally between day and night; in the climate, it also has obvious characteristics. In addition to the Qingchun-Tibet Plateau, northeast, northwest, and northern North China, the country has entered a bright spring season. In the spring, on the vast land, there will be green willows, long grasshoppers, wheat joints, and rapeseed flowers. 

 "Monthly 72nd Settlement": "In the mid-February, the mid-February is divided into half-years and half of the 90-day period. Therefore, it is said to be divided. Autumn is synonymous." Han Dong Zhong Shu "Spring and Autumn Fan Yin and Yang In and out: "As for the month of Zhongchun, Yang is in the east, Yin is in the west, and it is called the vernal equinox. The equinox is also half of yin and yang. Therefore, the day and night are average and cold and flat." The phenomenon of phenology in the ancient Yellow River basin was corresponding to "The mysterious bird arrived, Lei Na evoked the sound and began to power" (see "Nong Sang Sung Tong"). At this time, winter crops in most parts of China entered the spring growth stage. Farming in central China: "Spring equinox rises and it is dry at a time." The equinox is also a traditional festival. In the Zhou Dynasty, the spring equinox had a sacrificial ceremony. "Book of Rites": "Sacrificial to the altar." Kong Ying Da sparsely: "that vernal equinox." This tradition is passed down from generation to generation. Qing Pan Rongzhen's "Ji Sheng Ji Sheng Sheng Ji Sheng": "Equinox Ji Ji, Qiu Ji sacrifices, is a national ceremony, the people can not be arrogant." Before and after the vernal equinox in the Qing Dynasty, the Gong Temple Ciyou ministers were sacrificed, the family is also the family Memorial ancestral hall. In the Southern Dynasties, Liang Zongxi wrote "Jing Chu Years Old": "Every day on the spring equinox, the people are cultivating ignoring fire on the house. There are birds such as black owls, first chickens and roaring, 'shelf racks', and this bird will enter the fields. "In the Ming Dynasty, Zichuan, Shandong Province, planted trees for spring wine and made cool. "Wenshui County" contains: "Equinox, brewing and mixing, and grafting."