As an important theoretical system in traditional Chinese Feng Shui (Chinese Geomancy), "San Yuan Jiu Yun", literally "the Three Cycles and Nine Periods", is deeply rooted in the ancient Chinese astronomy, geography and philosophical thought, which is especially closely linked to the Bagua of Yi Jing (the Book of Changes), “He Tu”, "Luo Shu" and other classics of the Traditional Chinese Learning. It is not only a kind of interpretation of the ancient people on the law of the change of time and space in the universe, but also plays a guiding role in the Feng Shui layout of the ancient buildings, which influences the people’s living environment and concept of life.
The concept of "San Yuan (the Three Cycles)" originates from the philosophical thinking of Yin and Yang and the Five Elements and the stem and branch method of chronology, and can be traced back to the views on heaven, earth and man stated in "Zhou Yi". According to legend, starting from the year of Jia Zi under the reign of Yellow Emperor (about 2697 B.C.), every 180 years is a "San Yuan" cycle, which is divided into the Upper, Middle and Lower cycles, corresponding to the three elements of heaven, earth and man, and symbolizing the cyclical changes and harmonious coexistence of heaven, earth and man.
The "Nine Periods " is to subdivide each "Yuan (major Cycle)" into three "minor period"; each minor period consists of 20 years, together for a major cycle of 60 years, that is, Period 1 to 9. The Nine Periods corresponds with the Bagua（Eight Trigrams）and nine stars of the nine palaces in the Xuankong Flying Star Feng Shui. Each star flies to the nine palaces in a different time period, and each prevails for twenty years, forming the situation of the nine stars ruling the fortune and horoscope in turn. 2024 - 2043 belongs to Period 9.
The “Three Cycles and Nine Periods” is related to the celestial bodies of Jupiter, Saturn and Mercury. The “Three Cycles and Nine Periods” is a product of the rotation of the solar system's planetary orbits in the universe. Specifically, Jupiter orbits the sun once every twelve years, and Saturn orbits the sun once every thirty years. Saturn meets Jupiter once in twenty years in a straight line during its rotational orbit. Saturn, Jupiter and Mercury meet in a straight line every sixty years. In addition, every one hundred and eighty years, the nine planets of the solar system will be on the same side of the sun, distributed in a small sector, forming the general assembly of the nine planets, and the ancient astronomers called it "the linked peals of nine stars".
This law of celestial operation is intrinsically linked to the division of time cycles of the “Three Cycles and Nine Periods”. Whenever the planets meet, they will have far-reaching effects on the Earth, interfering with the Earth's magnetic field and even triggering natural disasters. Therefore, the changes in the cycles of “Three Cycles and Nine Periods” are closely related to the operating laws of celestial bodies such as Jupiter, Saturn and Mercury.
