What Are the Heavenly Stems and Earthly Branches?
The Heavenly Stems and Earthly Branches, or "stems and branches" for short, are a system of symbols the traditional Chinese calendar uses to record the year, month, day, and hour — and they are the most basic elements of BaZi. The system is made up of two sets of symbols, the "Ten Heavenly Stems" and the "Twelve Earthly Branches," which pair together and cycle to form a complete coordinate of time. Understanding stems and branches is the first step to reading BaZi.
The Ten Heavenly Stems, the Five Elements, and Yin-Yang
The ten Heavenly Stems, in order, are: Jia, Yi, Bing, Ding, Wu, Ji, Geng, Xin, Ren, and Gui. Each stem corresponds to one of the Five Elements and carries a yin or yang polarity — odd positions are yang, even positions are yin:
- Jia — yang wood, Yi — yin wood
- Bing — yang fire, Ding — yin fire
- Wu — yang earth, Ji — yin earth
- Geng — yang metal, Xin — yin metal
- Ren — yang water, Gui — yin water
The Twelve Earthly Branches and the Zodiac
The twelve Earthly Branches, in order, are: Zi, Chou, Yin, Mao, Chen, Si, Wu, Wei, Shen, You, Xu, and Hai — corresponding neatly to the twelve familiar zodiac animals:
- Zi — Rat, Chou — Ox
- Yin — Tiger, Mao — Rabbit
- Chen — Dragon, Si — Snake
- Wu — Horse, Wei — Goat
- Shen — Monkey, You — Rooster
- Xu — Dog, Hai — Pig
How Stems and Branches Form the Sexagenary Cycle
The Heavenly Stems and Earthly Branches pair up two by two — for example "Jia-Zi, Yi-Chou, Bing-Yin…" — starting from the first stem matched with the first branch and pairing on down in order. Because the least common multiple of ten and twelve is sixty, one full round of stem-and-branch combinations comes to exactly sixty pairs, known as the "sexagenary cycle" (the sixty jiazi). Every sixty years, sixty months, sixty days, or sixty hours, the stems and branches return to their starting point and begin again.
The Role of Stems and Branches in BaZi
"BaZi" is really just the four moments of a person's birth — the year, month, day, and hour — each expressed with a "Heavenly Stem plus Earthly Branch" pair. The year, month, day, and hour each take up one pillar, together called the Four Pillars; each pillar has one stem and one branch, four pillars totaling eight characters — which is where the name "BaZi" (eight characters) comes from. By analyzing the elements, yin-yang, and relationships among these eight characters, a practitioner can sketch out a person's innate traits and the direction of their fortunes.
The stems and branches may look complicated, but once you first memorize the elements of the stems and the zodiac animals of the branches, then understand how the two pair up, you can build a solid foundation and gradually step into the world of BaZi.