What is BaZi? The Four Pillars, where they come from and where they stop

Eight characters, four pillars

BaZi (八字) literally means “eight characters”. It is a way of writing down the moment of birth: the year, month, day and hour are each expressed as a pair, one heavenly stem and one earthly branch. Four pairs make eight characters, which is why it is also called the Four Pillars. A chart might read 辛巳 甲午 癸亥 己未, and that is the whole thing.

There are ten stems (甲 乙 丙 丁 戊 己 庚 辛 壬 癸) and twelve branches (子 丑 寅 卯 辰 巳 午 未 申 酉 戌 亥). Pairing them off produces a cycle of sixty combinations, the sexagenary cycle. China has used this cycle for more than three thousand years to count years and days, and you will find it in calendars, farming almanacs, traditional medicine and architecture. BaZi simply applies the same notation to the moment someone is born.

Where it comes from

The traditional account goes like this. In the Tang dynasty, Li Xuzhong worked with the year, month and day. In the Song dynasty, Xu Ziping added the hour and settled the four-pillar format, which is why the school is often called the Ziping method. Later works such as Yuanhai Ziping, Sanming Tonghui and Ditian Sui collected rules and case studies into something like a canon.

Much of that history was written down long after the fact, and the details are hard to verify. What we can say safely is that BaZi is a folk tradition that has been edited, argued over and re-edited for centuries. There is no single authoritative version, and serious practitioners disagree about plenty.

How the four pillars are calculated

Building a chart is mostly a calendar problem. Belief does not come into it.

• The year pillar changes at Lichun, the start of spring in early February, not at Lunar New Year. Someone born in January belongs to the previous BaZi year.
• The month pillar changes at the solar terms called jie (节), such as Lichun, Jingzhe and Qingming. BaZi months therefore match neither calendar months nor lunar months.
• The day pillar comes from counting days through the sixty-day cycle.
• The hour pillar divides the day into twelve two-hour periods. Traditionally you first convert clock time into true solar time: the further a birthplace is from the standard meridian of its time zone, the larger the correction, and the equation of time adds a seasonal shift on top.

Which is why the same birth date in two different cities, or half an hour apart, can give different hour pillars. A trustworthy calculator asks for your birth city for exactly this reason.

What people read in a chart

Once the pillars are set, the usual first step is the Day Master, the stem of the day pillar, which stands for “you”. The other seven characters are read as relationships to it, known as the ten gods. After that comes the balance of the five elements across the whole chart. All of this is a way of reading one table, and different schools emphasize different things.

Knowfive translates those readings into plainer language. The Day Master becomes an Eastern personality type, the element distribution becomes your element balance, and the ten-year luck pillars become Decade Seasons. Every statement can be traced back to a specific item on the chart.

What it is good for, and what it is not

BaZi works well as:

• A culturally rich vocabulary for reflecting on your temperament and working rhythm.
• A conversation starter with friends and family, with words for describing how you differ.
• A window into how a centuries-old folk knowledge system is organized.

It is not suited to:

• Judging health, investment results or other people’s private lives.
• Making decisions for you. A chart describes tendencies; the choice stays with you.
• Being cited as science. There is no reliable evidence that birth time predicts life outcomes.

Our attitude is to treat BaZi as one lens for looking at yourself, a bit like reading a character sketch someone else wrote. Some lines will fit and some will not, and that is fine.

Try it yourself

Knowfive offers a free BaZi calculator. You enter a birth date and pick a birth city, and it returns your four pillars, your Day Master and your element balance. The calculation runs in your browser and your birthday is never uploaded. From there you can read about your personality type, or just enjoy it as a small tool.

Written by our content team and still awaiting review by a BaZi consultant. For cultural curiosity and self-reflection only; not a prediction or professional advice.