What is BaZi (Four Pillars of Destiny)? - the Eastern birth chart explained

BaZi, also called the Four Pillars of Destiny (saju in Korean), writes a birth moment as four pairs of calendar characters - year, month, day and hour - and then looks at how their five elements balance. It is built from a calendar, not from a map of the sky, and this page builds one chart from start to finish.

Eight characters taken from the calendar

The traditional East Asian calendar labels every year, every month, every day and every two-hour period with a pair of signs: one of the 10 heavenly stems (甲, 乙, 丙 ... 癸) on top and one of the 12 earthly branches (子, 丑, 寅 ... 亥) below. The pairs run in a fixed cycle of 60, starting at 甲子. A moment of birth therefore gets four pillars, and four pillars of two characters make eight - which is what the romanized name BaZi means: eight characters.

Each stem and each branch carries one of the five elements (Wood, Fire, Earth, Metal, Water) and a yin or yang polarity. Branches also hold hidden stems, weighted by how many days of their month each one rules. Nothing in the chart is observed in the sky at the moment of birth; the characters are read off four counters. The year counter turns at lichun, the month counter at the twelve jie terms, the day counter runs continuously through the sixty-day cycle, and the hour counter follows twelve double hours.

BaZi and Western astrology side by side

People often meet BaZi as "the Chinese horoscope", but its structure is quite different from the Western birth chart. The table compares what each system records. It describes method only; neither column is a claim that the system predicts anything.

What each system records (BaZi values from the haru engine facts; Western column describes the usual tropical zodiac method)
	BaZi (Four Pillars)	Western astrology
What is recorded	Calendar labels: a stem and a branch for the year, month, day and hour	Positions of the sun, moon and planets along the zodiac
Building blocks	10 stems, 12 branches, 60 stem-branch pairs, five elements	Zodiac signs, planets, houses, aspects
The "sign" people know	Day master: the stem of the day pillar (庚 in the example below)	Sun sign: the zodiac sign the sun occupies
Where the year begins	Lichun, sun at 315 degrees (2026: 2026-02-04 05:02 KST)	The spring equinox, sun at 0 degrees (2026: 2026-03-20 23:46 KST)
When the month changes	At the 12 jie terms: 315, 345, 15 degrees and every 30 degrees on	The sun changes sign at 0, 30, 60 degrees... - the longitudes of the qi terms
Birth time	Needed for the hour pillar; without it the chart has six characters	Needed for the rising sign and the houses
Birth place	Longitude, to turn clock time into true solar time (Seoul in May: -28 minutes)	Latitude and longitude, to draw the houses
How parts relate	Ten gods: each stem named by its relation to the day master	Houses and the angles (aspects) between planets
Balance	Share of each of the five elements, hidden stems included	Spread of planets across signs and elements

A worked example: Seoul, 15 May 1990, 14:30

Here is how the haru engine builds the chart for a birth in Seoul at 14:30 local clock time on 15 May 1990. Each step uses one rule.

Year: lichun of 1990 fell on 1990-02-04 11:14, so May is already inside the new year. (1990 - 4) mod 60 = 6, the seventh pair of the cycle: 庚午, the year of the Horse.
Month: in mid-May the sun has passed lixia, the jie term that opens the 巳 month. By the five-tiger rule a 庚 year starts its months at 戊寅, so the 巳 month is 辛巳. The birth sits about 222.4 hours from the nearest jie term, so the month is not in doubt.
True solar time: Seoul lies at 126.978 degrees east, west of the 135-degree meridian its clock uses. With the equation of time (+3.7 minutes that day) the correction is -28 minutes, so 14:30 on the clock is 14:01 by the sun.
Day: the continuous sixty-day count gives 庚辰 for that date.
Hour: 14:01 falls in the 未 double hour (13:00-15:00). By the five-rat rule a 庚 day starts its hours at 丙子, so the 未 hour is 癸未.

The four pillars of example A (Seoul 1990-05-15 14:30) with hidden stems and ten gods
Pillar	Characters	Stem element	Branch element	Hidden stems (days)	Stem seen from 庚
Year	庚午	yang Metal	Fire	丙10 己9 丁11	Companion 比肩
Month	辛巳	yin Metal	Fire	戊7 庚7 丙16	Rob Wealth 劫財
Day	庚辰	yang Metal	Earth	乙9 癸3 戊18	the day master itself
Hour	癸未	yin Water	Earth	丁9 乙3 己18	Hurting Officer 傷官

From characters to balance

Counting only the eight visible characters gives Wood 0, Fire 2, Earth 2, Metal 3 and Water 1. The engine then adds the hidden stems, each by its days out of 30, and counts the month branch twice because it stands for the season. The shares come out as Wood 4.4%, Fire 23%, Earth 21.9%, Metal 38.5% and Water 12.2%.

The day master is 庚, yang Metal. Its support is its own element plus the element that produces it: Metal 38.5 + Earth 21.9 = 60.4. The month branch 巳 is Fire, neither Metal nor Earth, so the season does not lend a hand and 8 points come off: 52.4. That lies between 40 and 55, which the engine calls balanced.

For a balanced chart, the useful element is the smallest of the three elements that draw on the day master: the one it produces (Water, 12.2), the one it controls (Wood, 4.4) and the one that controls it (Fire, 23). Wood is the smallest, and it is also missing from the visible characters. The tradition reads Wood as the element this chart would most welcome, and haru turns that into gentle daily suggestions such as green vegetables - lifestyle tips, not predictions.

How to read a chart calmly

A chart is a symbolic snapshot of the calendar at one moment. The tradition uses it as a vocabulary for talking about temperament, rhythm and balance, and different schools weigh the same eight characters differently. Nothing on this page says what will happen to anyone. Read the words "strong", "weak" or "useful" as technical terms of the method, the way a musician says a chord is major or minor.

Questions

Is my day master the same as my zodiac animal?

No. The animal comes from the year branch (the Horse, 午, for 1990 after lichun). The day master is the stem of the day pillar - 庚 in the example - and the tradition treats it as the centre of the chart.

Why does the BaZi year start in February?

The year pillar turns at lichun, when the sun reaches 315 degrees. In 2026 that was 2026-02-04 05:02 KST: a Seoul birth at 03:00 that morning has the year 乙巳, one at 09:00 has 丙午.

Do I need an exact birth time?

Only for the hour pillar. Without a time the chart has six characters; haru then uses noon for the year and month and flags births that fall on a term day.

Is BaZi the same thing as Korean saju?

Yes. Saju (四柱, four pillars) is the Korean name for the same method, using the same stems, branches and calendar rules.