Gan Zhi is the combined name for the Heavenly Stems and Earthly Branches — the foundational symbol system of the traditional Chinese calendar and of destiny analysis. Each of a BaZi chart's four pillars (year, month, day, hour) is one stem paired with one branch — hence "Four Pillars, Eight Characters."
Stems and Branches
- **Ten Heavenly Stems:** Jia, Yi, Bing, Ding, Wu, Ji, Geng, Xin, Ren, Gui — five yang, five yin, each assigned an element.
- **Twelve Earthly Branches:** Zi, Chou, Yin, Mao, Chen, Si, Wu, Wei, Shen, You, Xu, Hai — corresponding to the twelve zodiac animals, twelve months, and twelve double-hours.
The Sixty Jiazi
The ten stems and twelve branches pair in sequence — Jia-Zi, Yi-Chou, Bing-Yin… — yang with yang, yin with yin, and one full cycle yields **60** combinations, the [sixty jiazi](/bazi/glossary/liu-shi-jia-zi). Each has its own [sound-element (Na Yin)](/bazi/glossary/na-yin). The cycle repeats every sixty years and is used to mark year, month, day, and hour.
Role in BaZi
- Gan Zhi is the smallest unit of chart-casting: convert the birth year, month, day, and hour into four stem-branch pairs and you have the eight characters.
- Stems govern the "shown," branches the "hidden" (hidden stems); a stem [roots](/bazi/glossary/tong-gen) in a branch and a branch becomes [transparent](/bazi/glossary/tou-gan) at the stems — the two interweave into the chart.
Significance in Chart Analysis
Understanding Gan Zhi is the first step in learning BaZi. Convert your birth time into the four stem-branch pillars with the [free BaZi calculator](/bazi/chart), and study it in the [BaZi learning center](/bazi/learn).