What is bazi (Four Pillars)?

Bazi (八字) means "eight characters." A chart has four columns, called pillars, for the year, month, day and hour of birth. Each pillar pairs one of ten heavenly stems with one of twelve earthly branches, so four pillars give eight characters.

The stems and branches run together in a fixed cycle of sixty pairs. In a chart, each character also carries one of the five elements and a yin or yang quality, and the other characters are read in relation to the stem of the day pillar, known as the day master.

The anthropologist Stéphanie Homola places bazi within mingli, the branch of Chinese divination that calculates fate from the calendar, and describes it as the mainstream method of that branch.

The year pillar usually changes at Lichun, the solar term that opens spring in early February, and the month pillar changes at set solar terms. The day pillar comes from an unbroken count through the cycle of sixty, and the hour pillar from the two-hour block of the birth.

A practitioner weighs how the elements support or restrain one another and follows a series of ten-year periods called luck pillars. Schools disagree on details as basic as when the day changes late at night, and on how to judge whether a chart is strong or weak.

The stems and branches themselves are very old. They appear as a working count in the oracle bone inscriptions of the late Shang state, around 1200 BCE, where they were used only to keep track of days. Using the cycle for years came much later, around the middle of the third century BCE.

The first clear account we found of a named person reading fate from these signs is an epitaph by the writer Han Yu for the official Li Xuzhong (李虛中), who died in 813 at the age of fifty-two. Han Yu says Li took the stems and branches of a person's year, month and day of birth, weighed how the five phases fed or overcame each other, and from that inferred length of life, rank and fortune. Lü Cai, who died in 665, had already attacked fate reckoning from the birth year and month.

That is three pillars. Editors of the Qing imperial catalogue pointed out that the epitaph stops at the day and leaves out the hour.

A book circulates as Li Xuzhong's work, but old copies name the legendary Guiguzi as author and Li only as commentator. The imperial editors suspected a Tang core with Song dynasty additions. Its later part speaks of four pillars, an idea they dated to the Song.

The Song is also when the name Xu Ziping (徐子平) appears. A commentary on the Luolu zi carries his name, and the catalogue says that people who calculate the eight characters came to be called ziping after him. Homola notes that from the Song period fate analysis spread from the court to the wider population.

Handbooks followed. A Yuan commentary on the Ziping tradition is dated to 1307. The Yuanhai Ziping (淵海子平) is listed as a Song compilation later revised in the Ming. In the Ming, the scholar Wan Minying, who passed the highest examination in 1550, compiled the Xingxue dacheng, and the large Sanming tonghui, probably also his, became the standard reference. The Ditian sui (滴天髓) is regarded as one of the most sophisticated treatises on the method.

In the twentieth century, modernizing campaigns labeled the practice superstition. From the late twentieth century it revived, particularly in Taiwan, Hong Kong, Singapore and Malaysia. In Taiwan divination specialists became more active in the 1970s and 1980s, and open consultation has been possible in mainland China since the 1980s.

Almost nothing is known about Xu Ziping. The imperial catalogue says his life cannot be documented. It treats him as a Northern Song author, then quotes the writer Liu Yu, who called him a hermit of the Five Dynasties named Juyi and said the practice called ziping really goes back to a late Song man named Xu Yansheng. The catalogue says it does not know what Liu based this on.

The authorship of the Yuanhai Ziping is similarly uncertain. English Wikipedia credits Xu Dasheng and calls him Xu Ziping, in an article short of citations. A Yuan preface quoted in the imperial catalogue names Xu Dasheng without saying he is Xu Ziping. We could not establish whether he is the Xu Yansheng of the catalogue, and we found no firm date for the first compilation.

Xu Ziping is traditionally credited with adding the hour pillar, and popular accounts also say he made the day stem the center of the reading. We did not find an early text that states either. The authorship of the Ditian sui is disputed as well.

The old books record what practitioners claimed a chart could show. They are not tests of those claims.