The historical origin of the twenty-four solar terms

Twenty-four solar terms are special festivals in the dry calendar, indicating the change of natural rhythm and establishing "December construction". At first, it was based on the movement of stars. The Big Dipper rotates circularly, and bucket handle rotates around the east, south, west and north, which is called one of the "years old" (Figure). Each rotation cycle begins in early spring and ends in severe cold.