This refers to a period of five days. The *Book of Documents* states: "There are three hundred and sixty-six days in a year; leap months are used to determine the four seasons and complete the year," which illustrates this principle.
Within one cycle, the Principal Movements (Zhu Yun, the fixed sequence of Five Phases Qi) are arranged sequentially below according to their positions, while the Guest Movements (Ke Yun, the variable sequence of Six Qi) circulate above with the Qi. The Guest Qi (Ke Qi) is superimposed upon the Principal Movements, and the Principal Qi (Zhu Qi) lies beneath the Guest Qi. It is precisely because the heavenly times and climatic conditions are not uniform that diseases among the people arise.