BaZi, 八字, means eight characters. A birth moment is written as four pairs of Chinese characters, and everything a practitioner says follows from the relationships between those eight.
It is also called 四柱, the Four Pillars of Destiny, and the two names describe the same object from different angles: four columns, eight characters.
The Four Pillars
One pillar each for the year, the month, the day and the hour of birth. Each pillar is a Heavenly Stem, 天干, written above an Earthly Branch, 地支.
Only two of the eight characters are independent. The month stem is derived from the year stem and the hour stem from the day stem, both by fixed arithmetic. Those are mechanics rather than doctrine, and knowing it removes some of the mystery from a chart: half of what looks like eight separate facts is bookkeeping.
The Ten Stems and the Twelve Branches
There are ten stems, and they are the five elements taken twice, once yang and once yin: 甲 yang wood, 乙 yin wood, 丙 yang fire, 丁 yin fire, 戊 yang earth, 己 yin earth, 庚 yang metal, 辛 yin metal, 壬 yang water, 癸 yin water.
There are twelve branches, and these are the ones people recognise, because each carries an animal and a two hour slot of the day.
- 子 Rat, 11pm to 1am, water. 丑 Ox, 1am to 3am, earth.
- 寅 Tiger, 3am to 5am, wood. 卯 Rabbit, 5am to 7am, wood.
- 辰 Dragon, 7am to 9am, earth. 巳 Snake, 9am to 11am, fire.
- 午 Horse, 11am to 1pm, fire. 未 Goat, 1pm to 3pm, earth.
- 申 Monkey, 3pm to 5pm, metal. 酉 Rooster, 5pm to 7pm, metal.
- 戌 Dog, 7pm to 9pm, earth. 亥 Pig, 9pm to 11pm, water.
The Vietnamese zodiac puts a cat in the fourth position rather than a rabbit, which is a useful reminder of the animals being a layer over the branches rather than the branches themselves.
One detail is genuinely unsettled and worth knowing, because it turns up in arguments. By its position in the list, 子 is yang. By its dominant hidden stem it is yin water. The same inversion applies to several branches, reference tables contradict each other over it, and practitioners have a phrase for the awkwardness rather than a resolution.
Sixty Pairs, and Where They Come From
Stems and branches pair off into a cycle of sixty rather than a hundred and twenty, because a stem and a branch have to match in polarity. Half the possible pairings never occur, which is why every pillar in every chart is polarity consistent.
The day count is remarkably old and remarkably continuous. Sexagenary day names appear on Shang oracle bones, and the day count has run unbroken since at least the eighth to fifth centuries BCE, which is checkable against recorded eclipses. Using the same cycle for YEARS is much later, with the earliest evidence from a tomb sealed in 168 BCE.
The current cycle began in 1984 and the next begins in 2044.
The Day Master
One of the eight characters is the reference point for all the others: the stem of the day pillar, called the 日主 or Day Master. It stands for the person, and every other character is read by its relationship to it.
This is the defining move of the system as it is now practised. The older three pillar method used the year stem for the self, and shifting the reference point to the day stem is what separates the method named after Zi Ping from what came before.
Five Elements, or Five Phases
The 五行 are usually translated as five elements, and the translation is misleading. They are not substances. They are processes, and sinologists have proposed five phases, five agents and five transformations to make the point.
Two relationships do most of the work. In the generating cycle wood feeds fire, fire makes earth, earth yields metal, metal carries water, water grows wood. In the controlling cycle wood breaks earth, earth blocks water, water quenches fire, fire melts metal, metal cuts wood.
Longer taxonomies of five relationships circulate, with terms for overacting and insulting. Those come mainly from Chinese medicine, where they describe pathology, and BaZi texts generally work with generating, controlling and draining without the extra vocabulary.
Hidden Stems
Each branch is held to contain one to three stems inside it, called 藏干 or 人元. They are ranked: a root, a middle and a residual.
Hidden stems matter more than their obscurity suggests, because they are how a practitioner decides whether an element in the chart has depth or is merely on the surface. They are also one of the places practitioners disagree most, and the disagreement is the subject of the companion guide.
The Ten Gods
十神, the Ten Gods, are not deities. They are the ten possible relationships between the Day Master and another stem: five elemental relations, each split by whether the polarity matches.
比肩 and 劫財: the same element as the Day Master. Shoulder to shoulder is a peer, and robbing wealth is a rival who takes from you.
食神 and 傷官: what the Day Master produces. The eating god is easy, benign output. The hurting officer is sharp output, talent with a taste for breaking rules.
偏財 and 正財: what the Day Master controls. Indirect wealth is unfixed, a windfall or a side income. Direct wealth is earned and steady.
七殺 and 正官: what controls the Day Master. Seven killings is pressure and challenge. Direct officer is legitimate authority, status and responsibility.
偏印 and 正印: what produces the Day Master. Indirect seal is unorthodox support, intuition and niche knowledge. Direct seal is orthodox support, education and protection.
Two details are worth carrying away. For wealth, officer and seal the naming runs the opposite way to intuition: 正, direct, attaches to the opposite polarity pairing, and 偏, indirect, to the matching one. And seven killings is called seven because counting along the ten stems from the Day Master, the controlling stem of the same polarity is the seventh.
The traditional glosses also carry their period. Direct wealth is read as a wife in a man’s chart and direct officer as a husband in a woman’s, and a modern practitioner will usually tell you so before using them.
Luck Pillars and the Flowing Year
大運, the luck pillars, are ten year periods laid over the natal chart. They run forward or backward from the month pillar depending on the polarity of the birth year together with sex, and the classical rule is compact: yang year men and yin year women go forward, yin year men and yang year women go back.
The starting age is counted, not chosen. Count from the birth to the nearest month boundary, forward or backward according to the direction, and convert at three days to the year. Somebody born nine days from the boundary starts their first luck pillar at three.
The rounding is not standardised. Some practitioners round to whole years, some carry the months and hours, and some write the exact handover date and give no age at all.
流年, the flowing year, is simply the actual sexagenary year. It is the same year for everybody and it is not arranged by sex or polarity, whatever some popular writing says. What differs is how a given year meets a given chart.
The Calendar Is Solar, Despite Appearances
This is the thing most people get wrong about BaZi, and the source of the confusion is a solar system written in the notation of a lunar calendar.
The year divides into twenty-four solar terms, at fifteen degree intervals of the sun along the ecliptic. Twelve of them, the 節, open the months. The other twelve sit at the midpoints and do the job of labelling lunar months and finding leap months.
So a BaZi month runs from one solar term to the next, and not from a lunar new moon and not from the first of a calendar month. The Tiger month opens at Li Chun, around the third to fifth of February. The Rabbit month opens at Jing Zhe, around the fifth of March. And so on around the year.
The boundary is the solar term to the minute. A birth a few minutes on either side of it has a different month pillar, and usually a different reading altogether.
One terminology trap, because it catches people reading official sources. The Hong Kong Observatory translates the midpoint terms as major and the month opening terms as minor, which reads backwards to anybody doing BaZi, where the minor ones are the operative ones.
Where the Year Begins Is a Three Way Argument
Li Chun, in early February, is the standard for the stem and branch calendar and therefore for BaZi, and it is settled inside the practice.
It is not the only convention in the world, and the alternative is not a mistake. The Chinese national standard for the agricultural calendar puts both the sexagenary year and the zodiac animal year at the first day of the first lunar month, and the Hong Kong Observatory publishes its calendar the same way. So somebody born in late January has one animal by the national standard and, quite possibly, another in a BaZi practitioner’s hands.
A third position puts the boundary at the winter solstice. It is a minority view, it is attested in silk manuscripts from the second century BCE, and some modern authors have revived it.
If your birthday falls in January or the first days of February, ask which boundary a practitioner uses. It is not a trick question and it changes your year pillar.
True Solar Time, and Why the Hour Pillar Is the Weakest
The hour pillar is the only one whose input is a clock reading, and a clock reading is a convention rather than a measurement of the sun. Turning one into a real solar time takes three corrections.
- Daylight saving, where it was in force. Mainland China observed it from 1945 to 1948 and again from 1986 to 1991, and not since.
- Longitude. The earth turns fifteen degrees an hour, so four minutes for every degree away from the meridian the time zone is built on.
- The equation of time, the annual wobble between clock noon and solar noon. It runs about sixteen and a half minutes ahead in early November and about fourteen minutes behind in the middle of February.
China is the sharpest illustration available, because one time zone covers the whole country. Clock time there is referenced to 120 degrees east. Kashgar sits near 76 degrees east, roughly forty-four minutes behind its own zone’s nominal sun, and Urumqi is offset by more than two hours. Xinjiang switched between two zones repeatedly between 1969 and 1986 and still keeps an unofficial local time alongside the official one, so a birth record from there might be in either.
Stack the corrections and they compound past an hour. A two hour branch flips on an error of about sixty minutes, roughly half the time. One practitioner source makes the point sharply: which legal time zone was in force in the birth year, and whether daylight saving applied, usually matter more than the longitude correction does.
The Hour Before Midnight
The 子 hour runs from eleven at night to one in the morning, straddling midnight, and there is a genuine unresolved dispute about which day the first half belongs to.
One position treats eleven at night as the start of the next day, because 子 is the first hour. The other keeps the current day until midnight, because the date changes at midnight. Practitioners have a saying about it: even an immortal struggles with the late 子 hour.
The consequence is the largest in this whole article. The two rules give different DAY pillars, and the day stem is the Day Master. A different Day Master means every one of the Ten Gods in the chart is different. The two rules disagree for exactly one hour a day, and inside it they produce two different readings of one person.
Combine the two sections. A birth recorded at a quarter past eleven at night in western China during the daylight saving years, corrected for the hour of daylight saving and for the longitude, lands near half past nine in true solar time: a different branch, and a different day under either rule. Two competent practitioners, one birth certificate, two entirely different charts.
What a BaZi Reading Does Not Establish
Start with an absence, because the absence is the finding. There is no body of scientific testing of BaZi to summarise. One peer reviewed study exists, with 148 participants, and its own primary measures found no significant correlations.
The adjacent evidence tests other chart systems and is worth knowing about. The strongest result is the time twins study, which took around two thousand people from a British birth cohort, all born within minutes of one another in London across one week in 1958, and compared them on more than a hundred measures from reading ability to occupation to accident proneness. They were no more alike than randomly paired strangers. The result aims at exactly the claim any birth chart system makes.
A double blind test of Western astrology published in 1985 reached a negative result, and a later reanalysis argued for a small effect. The reanalysis appeared in astrology aligned journals and is not accepted in mainstream psychology. Naming both is more honest than naming either.
There is also work on why a reading feels accurate. Generic personality profiles presented as astrological are widely accepted as personal, and one cross cultural study found the effect largely disappeared once education and psychological knowledge were controlled for.
The tradition also has a problem of its own, and practitioners concede it openly. Twins born in the same two hour period have identical eight characters, and if they are the same sex their luck pillars run the same direction, so they have identical charts. Chinese practitioner writing calls twins the blind spot of the subject. The same objection applies to everybody else born in the same two hour window anywhere on earth.
The resolution ceiling is the underlying reason. The finest unit is a two hour period, giving fewer than thirteen million possible charts for eight billion people, and the system takes no input for place of birth, parentage or circumstance. Longitude enters only as a correction to the clock and never as a variable in the chart.
And every pillar below the year depends on the accuracy of a record. A chart built from a remembered or rounded birth time is a chart of the record rather than of the birth.
What a reading offers once all of this is understood, and where it stops, is in what readings tell you, and where their limits are.
One Last Thing, Which Cuts the Other Way
The earliest stratum of this tradition framed itself morally rather than predictively. A second century text describing fate reckoning gives its purpose as encouraging good conduct and the cultivation of virtue.
A practitioner working in the same spirit is doing something different from one telling you what will happen, and the difference is worth asking about before you book.
Why two trained practitioners reach different conclusions from identical eight characters is the subject of BaZi schools and methods.