The establishment of the ancient branch calendar provided decisive conditions for the formation of festivals. Ancestor belief and sacrificial culture were important factors in the formation of ancestral worship custom in Qingming Festival. According to the research results of modern anthropology and archaeology, the two most primitive beliefs of human beings are the belief in heaven and earth and the belief in ancestors. Tomb-Sweeping Day Qi's characteristics, ancestral beliefs and sacrificial culture evolved into Tomb-Sweeping Day and became a fixed custom.
Tomb-Sweeping Day is one of the twenty-four solar terms in the trunk and branch calendars, which indicates the change of seasons. At this time, it is a good time for outing in the suburbs (spring outing) and Qingming (grave-sweeping sacrifice). The old and the new spit out the old, the temperature rises, everything is clean and tidy, and the earth presents a quiet image of spring.