General concepts

BaZi (Four Pillars of Destiny)

Also known as: ba ziba-zifour pillars of destinyfour pillarseight characters八字四柱zi pingchinese astrologychinese birth chartbazi chartbazi readingsajusaju paljashichu suimei

BaZi, the Four Pillars of Destiny, is the traditional Chinese way of reading the moment of birth: the year, month, day and hour each form a pillar of one Heavenly Stem and one Earthly Branch, eight characters in all.

The name BaZi (八字) means "eight characters". A BaZi chart is not a map of planets but a table of four columns. Each column, called a pillar, stands for one unit of time at birth: the year, the month, the day and the two-hour period. Every pillar is written with two signs, a Heavenly Stem on top and an Earthly Branch below. The ten stems and twelve branches combine into a repeating cycle of sixty pairs, the same cycle the Chinese calendar has used to count days and years for more than two thousand years.

The method grew out of older calendar divination. Tradition links an early form, read from the year, month and day, to Li Xuzhong in the Tang dynasty. In the Song dynasty Xu Ziping added the hour and moved the centre of the reading from the year to the stem of the day, which is why the classical method is also called Zi Ping. Later texts such as the Yuan Hai Zi Ping, the San Ming Tong Hui and the Di Tian Sui are still studied today. Close relatives of the system are known in Korea as Saju and in Japan as Shichū Suimei.

The pillars follow the solar year, not the lunar calendar. The BaZi year begins at Li Chun, the Start of Spring, when the Sun reaches 315 degrees of ecliptic longitude, usually on 3, 4 or 5 February. The lunar New Year can fall weeks earlier or later, so someone born in late January belongs to the previous BaZi year. Each month begins at one of the twelve Jie solar terms, the day pillars run through an unbroken sixty-day cycle, and the hour pillar follows twelve double hours, starting with the Zi hour at 23:00. Schools differ on whether the day changes at midnight or at 23:00 and on whether to use clock time or local solar time.

The popular Chinese zodiac sign is only one of the eight characters: the branch of the year pillar. Two people born in the same Year of the Dragon share that branch, while their month, day and hour pillars can be completely different. The tradition reads the year pillar as roots, family background and the wider social world, the month as upbringing and the season of birth, the day as the person and their closest partnership, and the hour as plans, children and later life.

The stem of the day pillar, the Day Master, is the reference point of the whole chart. Every other stem, including the stems hidden inside the branches, is related to it through the five phases and through yin and yang, which gives the Ten Gods. The tradition also looks at how many signs of each phase the chart holds, at the season of birth, and at combinations and clashes between the pillars. More advanced work judges the strength of the Day Master, the structure of the chart (Ge Ju), the useful phase (Yong Shen) and the ten-year luck pillars (Da Yun), and schools often disagree on those rules.

BaZi is a symbolic system and a cultural tradition, not a science, and there is no evidence that eight characters fix anyone's character or events. Its language works best as a way to reflect on temperament, rhythms and choices.

The free BaZi calculator in AstroSensus shows the four pillars with their stems and branches, the Day Master, the hidden stems, the Ten Gods, the count of the five phases and the basic combinations and clashes, and it names the conventions it used. It also shows the luck pillars (Da Yun) and the yearly and monthly pillars. It does not assess the strength of the Day Master, the chart structure (Ge Ju) or the useful phase (Yong Shen).