Chinese Astrology

Popular Western presentation of Chinese astrology reduces it to a birth-year animal, which is roughly like reducing Western astrology to a Sun sign, and misses what practitioners actually do.

The working method is Bazi, the eight characters, also called the Four Pillars of Destiny. Each of the year, month, day and hour of birth is expressed as a pair, one of ten Heavenly Stems and one of twelve Earthly Branches, giving eight characters in total. The twelve branches are the familiar animals; the ten stems are the five agents in yin and yang polarity. Stems and branches run together in a repeating cycle of sixty combinations, which is the basic unit of Chinese calendrical reckoning and is attested in use for well over two thousand years.

The five agents, Wood, Fire, Earth, Metal, Water, are the analytical core. They stand in fixed relations: each generates the next in one sequence and controls another in a second, so wood feeds fire and water quenches it. The reader assesses the balance of agents across the eight characters, identifies which the day stem most needs or has in excess, and reads the chart accordingly. Luck cycles of ten years are then derived from the month pillar and read against the natal balance for timing.

A separate and equally serious system, Zi Wei Dou Shu, the purple star method, places named stars into twelve palaces and is read quite differently.

Two practical points matter. The reckoning uses the solar terms, so the astrological year begins in early February at the start of spring rather than at lunar new year, and a person born in late January belongs to the previous year's pillar. And the hour pillar covers a two-hour double hour, so the birth time is required but need not be exact to the minute.

What distinguishes Chinese astrology from the Western tradition is that it is not a specialism at all. Yin and yang, the five agents and the stem-branch cycle are the shared framework of calendar, medicine, divination, geomancy and statecraft, and a Bazi reading uses exactly the same apparatus as a diagnosis in traditional Chinese medicine or a siting in feng shui.

The system took its recognisable form under the Han dynasty, when correlative cosmology was systematised into state orthodoxy: five agents matched to directions, seasons, colours, organs, flavours, tones and dynasties, so that the whole of experience could be laid out on a single grid. The sexagenary cycle is older, appearing in Shang oracle bone inscriptions for counting days. Bazi as a personal method is usually credited to Xu Ziping in the tenth century, which is why the method is often called the Ziping system; earlier personal astrology in China worked from the year pillar alone.

The imperial state maintained an Astronomical Bureau whose work was simultaneously calendrical, astronomical and ominous, and access to some of this material was legally restricted, since prediction about the dynasty was a political act.

Practitioners today read a chart for temperament, career suitability, health tendencies, compatibility and the timing of favourable and unfavourable periods, and the compatibility application is the one most visible in popular culture across East Asia, to the point that birth rates measurably dip in Dragon and Tiger years in several countries, an effect demographers have documented. That is a real social consequence of the belief, and it is a different thing from evidence for the system.

The tradition remains woven into ordinary life in China, Taiwan, Hong Kong, Vietnam, Korea and Japan through festivals and the naming of years, and professional Bazi consultation is a substantial commercial practice.

The twenty-four jieqi, the solar terms, divide the tropical year into arcs of fifteen degrees of solar longitude. They are solar, not lunar, and they are the part of the Chinese calendar that keeps the agricultural year in step with the seasons while the lunar months drift against it.

Because they are cut at fifteen-degree intervals from the vernal point, every second solar term falls on a multiple of thirty degrees, and thirty degrees is the width of a tropical zodiac sign. The correspondence is therefore exact rather than approximate. Chunfen, the spring equinox, begins at zero degrees, which is the cusp of Aries. Xiazhi, the summer solstice, begins at ninety degrees, the cusp of Cancer. Qiufen begins at one hundred and eighty, and Dongzhi at two hundred and seventy.

The twelve terms falling on the cusps are the zhongqi, the principal or middle terms; the twelve falling halfway between are the jieqi proper, the sectional terms. The two alternate.

The alternation does real calendrical work. A lunar month must contain the zhongqi assigned to it, and a lunar month that contains none becomes an intercalary month, repeating the number of the month before it. This is the rule that keeps the Chinese lunisolar calendar aligned, and it is why leap months fall where they do rather than at a fixed point in the year.

The exactness of the sign correspondence is a consequence of arithmetic, not a coincidence or a later harmonisation. Both systems cut the same tropical circle, one into twenty-four parts and the other into twelve.

What the two systems do with their divisions has nothing in common. The solar terms name weather and agricultural work. The tropical signs carry an entirely separate body of meaning. They share a set of boundaries and nothing else.