What is the astronomical basis of 60 years of Jiazi?

Jiazi chronology is based on "astronomy".

1 Jupiter is the largest planet in the solar system, and the Jiazi chronology is the result of observation and calculation.

The period of revolution of Jupiter is 4332.589 days, which is about 1 1.86 years. The ancients began to calculate from 12, and the direction that Jupiter turned every year was one of the "earthly branches". These twelve positions are also the origin of the zodiac.

Saturn's period of revolution is 10759.2 days, which is about 29.5 years. The ancients counted every 30 years.

Saturn orbits once every twenty years and meets Jupiter. The encounter between Jupiter and Saturn has a great influence on the earth.

It is a kind of luck that Saturn and Jupiter meet once every 20 years, and nine planets match nine kinds of luck. According to the law of celestial bodies, the least common multiple of Jupiter's revolution 12 years and Saturn's revolution of 30 years is 60 years, which is the origin of the geomantic chronology.

In ancient society, the royal family recorded astronomical phenomena at the same time, replacing astronomical chronology and entering people's normal life. After that, although the folk did not record the astronomical phenomena, they still used this method, that is, the 60-year chronology.