What is BaZi? The Four Pillars, explained

BaZi (八字, "eight characters") is a Chinese system that describes a moment in time — usually a birth — with the calendar the tradition has kept for over two thousand years. The moment is written as four pillars: year, month, day and hour. Each pillar has two characters, a Heavenly Stem on top and an Earthly Branch below, which makes eight characters in all. That is why the system is also called the Four Pillars of Destiny (四柱).

The calculation is pure calendar arithmetic. Everything that follows — the reading — is a traditional way of looking at the balance in those eight characters. It is a reflective practice, not a science, and nothing in a chart decides what will happen to you.

Stems and branches

There are ten Heavenly Stems (天干): 甲 乙 丙 丁 戊 己 庚 辛 壬 癸. Each belongs to one of the five elements (wood, fire, earth, metal, water) and is either yang or yin — 甲 is yang wood, 乙 is yin wood, and so on.

There are twelve Earthly Branches (地支): 子 丑 寅 卯 辰 巳 午 未 申 酉 戌 亥. They are the twelve animals of the zodiac, and each one also carries one to three "hidden stems" (藏干) that give it a more mixed character.

Pair stems and branches in order and you get a cycle of sixty (六十甲子). Years, months, days and two-hour periods all run through this cycle, which is why any moment can be written as four stem-branch pairs.

How each pillar is found

• Year pillar. The BaZi year begins at the Start of Spring (立春, around 4 February), not on 1 January and not at Lunar New Year. Someone born on 1 February 2027 still has the 丙午 year pillar of 2026.
• Month pillar. Months follow the twelve "node" solar terms (節), so each month begins on a precise astronomical moment — 寅 month starts at the Start of Spring, 卯 month at the Awakening of Insects (驚蟄), and so on. The month stem follows from the year stem.
• Day pillar. Days run through the sixty-cycle without a break, so the day pillar is a matter of counting.
• Hour pillar. The day is divided into twelve two-hour periods (時辰), starting with 子 hour at 23:00. The hour stem follows from the day stem. Practitioners differ on whether the day changes at 23:00 or at midnight; our calculator lets you choose and shows which convention it used.

Because the month and hour boundaries depend on the sun, a careful chart also corrects clock time to true solar time — the time the sun actually shows where you were born. See why true solar time matters.

The Day Master

The stem of the day pillar is called the Day Master (日主). Traditionally it stands for the person themselves, and the other seven characters are read in relation to it: which elements support it, which drain it, which it controls. See the ten Day Masters.

What a reading looks at

• Element balance. How strongly each of the five elements is present, weighting the month branch most because it sets the season.
• The Ten Gods (十神). Each stem's relationship to the Day Master — Resource, Output, Wealth, Officer and Companion, each in a yin and a yang form. They are the vocabulary readers use to talk about support, expression, money, structure and peers.
• Branch interactions. Clashes, combinations and harms between branches, which readers treat as points of tension or cooperation.
• Luck pillars and years. A sequence of ten-year "luck pillars" (大運) starts in childhood, and each calendar year brings its own pillar. Readers compare these with the birth chart to describe changing emphasis over time. See how luck pillars are calculated.

What a chart can't tell you

A BaZi chart is a structured way to think about temperament, timing and priorities. It does not predict illness or lifespan, it is not financial or legal advice, and it does not fix anyone's fate. The same chart is shared by everyone born in the same two-hour window in the same place. Read it the way you might read a thoughtful essay about yourself: keep what helps, question the rest.

Calculated in code

On this site every pillar is calculated by code from your birth date, time and place — the AI only writes prose about a chart that has already been computed, and it is not allowed to change it. If a birth time is unknown, the hour pillar is left out rather than guessed.