The name: eight characters, four pillars
In Chinese the practice is usually called 八字 bāzì, literally “eight characters”, or 四柱 sìzhù, “four pillars”. Both names describe the same object. A Chinese calendar date is written with two characters for the year, two for the month, two for the day and two for the double-hour, giving eight characters arranged in four columns. Each column is a “pillar”. A third name you will meet in older books is 子平 Zǐpíng, after Xu Ziping (徐子平), the Song-dynasty figure traditionally credited with shaping the method used today; that is why many classical titles contain the words “Zi Ping”.
In English the practice is often marketed as “Four Pillars of Destiny”. On this site we use the plainer “Bazi” or “Four Pillars”, because the classical texts themselves are mostly concerned with describing the balance of a chart, and because we do not present Bazi as a method of predicting events.
What the four pillars are
Each pillar is made of one heavenly stem (天干) written on top and one earthly branch (地支) written underneath. There are ten stems and twelve branches. Pairing them in order produces a cycle of sixty combinations, 甲子 jiǎzǐ through 癸亥 guǐhài, and the same sixty-pair cycle is used to count years, months, days and hours. A chart therefore looks like this:
| Hour | Day | Month | Year | |
|---|---|---|---|---|
| Stem | 丙 | 庚 | 丁 | 辛 |
| Branch | 子 | 午 | 酉 | 卯 |
That example is the chart recorded for the Qianlong Emperor, born in 1711. Chinese books write the pillars from right to left — year, month, day, hour — and so do most calculators. Every character carries one of the five elements (wood, fire, earth, metal, water) and a yin or yang polarity. Branches also contain one to three hidden stems, so a chart has more elemental information than its eight visible characters suggest.
The classical system singles out the stem of the day pillar, called the Day Master (日主 or 日元), as the point of reference for the person. Every other stem in the chart is then labelled by its relationship to the Day Master — these labels are the ten gods. The one-line summary of the method in the Ming-dynasty manual Yuan Hai Zi Ping is:
以日为主，年为本，月为提纲，时为辅佐。“Take the day as the master; the year is the root, the month is the governing axis, and the hour is the assistant.”— Yuan Hai Zi Ping 《淵海子平》, 论日为主. Original text: Wikisource · also on ctext.org (different edition). Translation: bazimethod.
The calendar behind Bazi
A common misunderstanding is that Bazi uses the Chinese lunar calendar. It does not, at least not for the pillars. The year and month pillars follow the Sun, through the twenty-four solar terms (节气). The Bazi year begins at 立春 lìchūn, “Start of Spring”, which falls around 4 February, not on 1 January and not on the Lunar New Year. Each Bazi month begins at one of the twelve “jie” (节) terms, roughly every 30.4 days. The day pillar simply counts days in an unbroken sixty-day cycle, and the hour pillar divides the day into twelve double-hours starting at 23:00.
Because the pillars change at exact astronomical moments, getting a chart right is mostly a matter of getting the time right. That means applying the correct time-zone and daylight-saving rules for the date and place of birth, and — in the classical view — converting clock time to local solar time. Our calculator shows each of those steps.
A short history
Using the stems and branches of a birth date to talk about a person’s fate is old. The texts themselves tell a story of two stages. The San Ming Tong Hui, a large Ming-dynasty compendium by Wan Minying (萬民英), credits the Tang-dynasty official Li Xuzhong with taking the day stem as the main point and reading the year, month and hour against it:
唐李虚中独以日干为主，却以年月时合看生克制化，旺相休囚，取立格局。此发前贤所未发，故今术家宗之。“Li Xuzhong of the Tang alone took the day stem as the master, and read the year, month and hour together with it for generation and control, strength and weakness, to establish the structure. This revealed what earlier worthies had not, and so the practitioners of today follow him.”— San Ming Tong Hui 《三命通會》, 卷二 · 论年月日时. Original text: Wikisource · also on ctext.org (different edition). Translation: bazimethod.
Yuan Hai Zi Ping tells it slightly differently: it says Li Xuzhong worked with all four pillars, and that the method of taking the day stem as master — “the Zi Ping theory” — arose in the Song dynasty:
至于宋时，方有子平之说；取日干为主，以年为根，以月为苗，以日为花，以时为果；以生旺死绝休囚制化，决人生休咎。“Only in the Song was there the Zi Ping theory: take the day stem as master, the year as the root, the month as the sprout, the day as the flower and the hour as the fruit; and use growth, peak, death, extinction, rest, confinement, control and transformation to decide good and bad in a life.”— Yuan Hai Zi Ping 《淵海子平》, 论日为主. Original text: Wikisource · also on ctext.org (different edition). Translation: bazimethod.
The two accounts disagree on who deserves the credit, which is typical of traditional histories, and we report both rather than choose. What they agree on is the structure that every modern calculator uses: four pillars, with the day stem at the centre.
The classical texts
Four books are cited again and again in Chinese Bazi writing, and we quote three of them on this site, each time with a link to the public-domain text on Wikisource so you can check the original line:
- 滴天髓 Di Tian Sui (“Drops from Heaven’s Marrow”): a short, dense verse text traditionally attributed to Jing Tu (京圖), with the commentary attributed to Liu Ji (劉基, Liu Bowen) of the early Ming; the authorship is uncertain. Its verses on the ten stems are still memorised.
- 淵海子平 Yuan Hai Zi Ping: a Ming compilation of earlier Zi Ping material, the classic statement of the Day-Master method, ten gods and hidden stems.
- 三命通會 San Ming Tong Hui: Wan Minying’s encyclopaedic Ming work, covering the calendar, the sixty-pair cycle, Na Yin, luck pillars and much more.
- 子平真詮 Zi Ping Zhen Quan: Shen Xiaozhan’s Qing-dynasty treatise on structures (格局) and the useful god. We could not find an online copy we could verify line by line, so we describe it but do not quote it.
The opening verse of Di Tian Sui gives a sense of the register these texts are written in:
欲識三元萬物宗，先觀帝載與神功。“If you wish to know the source of the three origins and all things, first observe the work of Heaven and its spirit-like effect.”— Di Tian Sui (Drops from Heaven’s Marrow) 《滴天髓》, 通天論. Original text: Wikisource · also on ctext.org (different edition). Translation: bazimethod.
Its commentary explains the “three origins” in Bazi terms: the day stem is the heavenly origin, the branches are the earthly origin, and the stems stored inside the branches are the human origin — the hidden stems.
日干為天元，地支為地元，支中所為人元。“The day stem is the heavenly origin, the earthly branches are the earthly origin, and what is held within the branches is the human origin.”— Di Tian Sui (Drops from Heaven’s Marrow) 《滴天髓》, 通天論. Original text: Wikisource · also on ctext.org (different edition). Translation: bazimethod.
How to approach Bazi today
We treat Bazi as a piece of Chinese intellectual and cultural history: a systematic way of describing time with stems, branches and the five elements, carried by a large body of literature. It can be studied, and it can be enjoyed, like Western astrology or the I Ching. There is no scientific evidence that a birth chart determines personality or events, and nothing on this site should be taken as a prediction or as advice about health, money, relationships or any other decision.
Within that frame, there are good and bad ways to do it. A good chart is calculated from the correct solar-term moments and the correct local time. A good explanation tells you which convention it follows and where its statements come from. That is the standard we try to meet: every page here cites the classical text it summarises, and our method page lists the tests the calculator passes and fails.
Where to go next
If you are new, read the guides in this order: heavenly stems, earthly branches, five elements, Day Master, ten gods. Then calculate your own chart and compare it with what you have read.
Keep learning
Classical quotations are copied from the public-domain texts on Wikisource; links let you check every line. English translations are our own. Traditional Bazi statements are reported as tradition, not as fact.