According to the terminology of numerology, the four groups of heavenly stems and earthly branches of year, month, day and hour are called "four pillars", that is, the heavenly stems and earthly branches of year are "year pillars", the heavenly stems and earthly branches of month are "moon pillars", and the day and year are called "four pillars". The heavenly stems and earthly branches of the hour are called "sun pillars", and the heavenly stems and earthly branches of hour are the "hour pillars". After the four pillars and eight characters are arranged, we can deduce the good, bad, and bad fortune of a person's life based on the ever-changing relationship between the five elements and the restraints between the eight characters. In the past, the eight-character fortune telling method mainly used the year pillar and combined with other three pillars for inference; there were also those based on the day pillar and combined with the other three pillars for inference; but the algorithm that mainly used the day pillar and combined with the other three pillars for inference is the most effective. authority. "Three Ming Tonghui" uses the sun pillar as the main method to promote fortune. The so-called taking the Rizhu as the mainstay means using the Rizhu and Heavenly Stems as the starting point for fortune telling when fortune-telling, and conducting analysis and inferences based on the complex relationship between the Rizhu and Heavenly Stems and the other stems and branches in the four pillars.