The BaZi chart
A BaZi chart (八字, literally “eight characters”) records a birth moment as eight characters. The eight are a stem and a branch for each of four pillars — year, month, day and hour. Each pillar is derived from a different thing, which is why they can disagree between calculators independently of each other.
| Pillar | Set by | Time frame | Where calculators can differ |
|---|---|---|---|
| Year | Li Chun, the first solar term | The absolute instant of birth | Chinese New Year used instead of Li Chun; near Li Chun, a corrected clock reading used instead of the birth instant |
| Month | The twelve month-opening solar terms (節) | The absolute instant of birth | A corrected clock reading used instead of the birth instant, for a birth near a term |
| Day | A continuous count through the sixty stem-branch pairs | True solar time | Where the day starts for a birth between 23:00 and midnight, on which schools disagree; and, for a birth near midnight, clock time used instead of true solar time |
| Hour | The position of the sun at the birthplace | True solar time | Clock time used instead of true solar time |
Year pillar
Set by where the birth instant falls relative to Li Chun, the first solar term — not Chinese New Year, and not the calendar year. Because the term is a single worldwide instant, the comparison must be made against the absolute time of birth, not any locally corrected clock reading. Worked boundary examples: 1988 Earth Dragon · 1981 Metal Rooster · 1996 Fire Rat · 1987 Fire Rabbit · 1991 Metal Goat · 1995 Wood Pig.
Month pillar
Set by the twelve month-opening solar terms (節) — not the mid-month terms (中氣). Like the year, it depends on an absolute astronomical instant.
Day pillar
A continuous count through the sixty possible stem-branch pairs — ten stems and twelve branches repeat together on a 60-step cycle. The only question is where the day starts, and schools disagree — see the conventions.
Hour pillar
Derived from the position of the sun at the birthplace, which is why it needs true solar time rather than clock time. At Hong Kong’s longitude the correction is negative every day of the year: the longitude part is a constant −23 minutes, and the equation of time swings the total between roughly −38 and −7 through the year. For a Hong Kong birth at 23:00 instead of noon, a clock reading of 23:00 is still 22:36 true solar time, and the hour branch is still the previous one. Once the branch is settled, the stem follows from the day stem — or the next day's, for a birth between 23:00 and midnight — and the full mapping is tabulated on the hour pillar page.
Why two calculators can disagree
Most often a site runs true solar time through the whole chart, which quietly produces the wrong year pillar for anyone born near Li Chun. The conventions state the rule this engine takes; the boundary cases show it happening.
How to read a BaZi chart, step by step
Casting settles the eight characters; interpretation is a separate step, and it starts with the day stem, not the zodiac animal.
- Find the Day Master. It is the stem, the top character, of the day pillar. Every other character is described by its relationship to that one, and there are ten possible Day Masters.
- Read it against its season. The month branch fixes which element rules, and so sets the climate every other character has to live in. The natal report's strength score starts from the Day Master's command of that season, then counts support: each branch besides the month's, and each stem besides the Day Master, that shares the Day Master's element or the element that produces it. The weighting is one of several in use — this project's own, not yet through practitioner review — and is stated in full.
- Name the other characters' roles. Each is classified by how its element and polarity stand to the Day Master: the ten gods (十神), the Ziping method's names for roles, not literal relatives. Hidden stems inside the branches take roles too. The complete sample report reads a full chart this way, chapter by chapter, naming the sources each chapter draws on.
- Count the element balance. One unit for each visible stem plus the primary qi hidden inside each branch. The sample also prints a fuller count that includes every hidden stem.
- Lay the luck pillars over it. Ten-year stem-branch pairs run in sequence from the month pillar, forward or backward by gender and the year stem's polarity, and each pillar's stem is read by its relationship to the Day Master. How the direction and starting age are worked out.
The natal report reads your own chart the same way.
Cast your own chart — free, no sign-up, with every correction shown. Or read what a Day Master is.