BaZi Chart Calculator
BaZi, also called the Four Pillars of Destiny, assigns a pair of Chinese sexagenary characters to the year, month, day and hour of birth. Eight characters in total. This page explains how those eight characters are derived, what each pillar represents, and the mistakes that most often produce a wrong chart.
Where the eight characters come from
There are ten Heavenly Stems and twelve Earthly Branches. Pairing them in sequence produces a cycle of sixty combinations, the sexagenary cycle. One combination is assigned to each of the four time units of birth, giving four pillars and eight characters.
Each Earthly Branch also conceals one to three Heavenly Stems, known as hidden stems. These determine how the elemental weight of a branch actually participates in the chart, and they are the step that turns eight visible characters into a full structure.
The month pillar follows solar terms, not lunar months
This is the single most common error. BaZi months are bounded by twelve of the twenty-four solar terms: the Tiger month begins at Start of Spring, the Rabbit month at Awakening of Insects, and so on. The pillar changes at the exact moment the term begins, which has nothing to do with the first day of a lunar month.
A person born on the third day of the first lunar month but before Start of Spring belongs to the previous year for both the year and month pillars. Anyone born near Start of Spring should verify this before anything else.
The hour pillar and true solar time
The day is divided into twelve two-hour periods, with the Rat hour straddling midnight. The stem of the hour pillar is derived from the stem of the day.
Clock time is zone time, which differs from true solar time at the place of birth. Fifteen degrees of longitude is roughly one hour, and the equation of time adds further drift. The combined offset can exceed an hour. For births close to the boundary between two periods, this is enough to change the hour pillar, so the longitude of the birthplace has to be taken into account.
Ten Gods and luck cycles
The stem of the day pillar is the reference point, called the Day Master. The relationship between every other stem and branch and the Day Master is classified into ten categories, the Ten Gods. This layer translates raw elemental interaction into readable language, and most of the classical literature is written in terms of it.
Decade luck cycles start from the month pillar. The starting age is calculated from the number of days between birth and the nearest solar term, and the sequence runs forward or backward depending on the polarity of the year stem and the gender. Each step covers ten years.
When the birth hour is unknown
A large share of people do not know their exact birth hour. The traditional handling is well established: cast the chart with three pillars only, using year, month and day, and suppress the readings that depend on the hour pillar. It is not to guess.
The other approach is to work backwards, comparing known life events against the twelve possible hour candidates and eliminating those that clearly do not fit. Both are more defensible than defaulting to the Rat hour, which simply invents a wrong pillar.
How to use it
- Enter the Gregorian date and time of birth, and the birthplace so that true solar time can be applied
- The chart is cast on the sexagenary calendar with hidden stems and elemental distribution
- Read the structure through the Ten Gods and the decade luck cycles