Ba Zi · Four Pillars

Bāzì (八字), the Four Pillars of Destiny, is a Chinese system of fate analysis that took its present form during the Song dynasty, when the scholar Xu Ziping moved the focus from the year of birth to the day. It builds on the much older sexagenary cycle of stems and branches, used in China for counting years and days for more than three thousand years.

It sits alongside other Chinese systems such as Zǐwēi Dǒushù (Purple Star astrology) and the I Ching. Unlike Western and Indian astrology, it does not observe the actual positions of the planets. It uses the calendar, which is itself built on the Sun and the Moon.

Ba Zi ("eight characters") encodes your birth moment as four pillars: year, month, day and hour. Each pillar stacks one of ten Heavenly Stems over one of twelve Earthly Branches — and every stem/branch is itself a blend of the five elements (Wood, Fire, Earth, Metal, Water) in yin or yang polarity.

Crucially, Ba Zi is solar and local: pillars change at solar terms and local true time, not midnight. Your Day Master — the day pillar's stem — is the central character; everything else in the chart is read as its environment.

A birth moment is written as four pillars: year, month, day and hour. Each pillar is a pair of one of ten Heavenly Stems and one of twelve Earthly Branches. The ten stems are the two phases (yin and yang) of the five elements: Wood, Fire, Earth, Metal and Water. The twelve branches are the twelve animals, each carrying hidden stems.

The month pillar changes not at the start of a calendar month but at one of twelve solar terms, the jiéqì, so the year pillar changes at the start of spring (around 4 February), not on 1 January or at the Lunar New Year. The hour pillar uses a two-hour period. Local time may need adjusting to true solar time.

The stem of the day pillar is called the Day Master and stands for the person. The chart is then read for the balance of the five elements and for the relations of each other stem to the Day Master. These are the Ten Gods (shí shén), such as Resource, Output, Wealth and Officer. Ten-year Luck Pillars are counted forward or backward from the month pillar.

Bāzì is a calendar system, not an astronomical one. It does not consult the planets. The hour pillar, and sometimes the day pillar for births near midnight, depends on a correct local time, and a different school may choose a different convention for the late-night hour.

The tradition itself recognises that schools differ in how they weigh the elements and judge the strength of the Day Master. A chart read by two practitioners can yield two different “useful elements”.