03 Ten Heavenly Stems, Twelve Earthly Branches, and the Sexagenary Cycle
Ten Heavenly Stems (10)
Jia, Yi, Bing, Ding, Wu, Ji, Geng, Xin, Ren, Gui
Twelve Earthly Branches (12)
Zi, Chou, Yin, Mao, Chen, Si, Wu, Wei, Shen, You, Xu, Hai
Common zodiac mapping: Rat, Ox, Tiger, Rabbit, Dragon, Snake, Horse, Goat, Monkey, Rooster, Dog, Pig
Yin-Yang and Five-Element Attributes
The ten heavenly stems carry both Yin-Yang and five-element attributes: Yang stems are Jia (Wood), Bing (Fire), Wu (Earth), Geng (Metal), Ren (Water); Yin stems are Yi (Wood), Ding (Fire), Ji (Earth), Xin (Metal), Gui (Water).
The twelve earthly branches also map to Yin-Yang and five elements: Zi and Hai are Water, Yin and Mao are Wood, Si and Wu are Fire, Shen and You are Metal, and Chen/Xu/Chou/Wei are Earth. Among them, Zi/Yin/Chen/Wu/Shen/Xu are Yang branches, while Chou/Mao/Si/Wei/You/Hai are Yin branches.
The Sexagenary Cycle (60-Cycle)
Heavenly stems and earthly branches are paired in sequence: Yang stems pair with Yang branches, and Yin stems pair with Yin branches, forming a repeating set of 60 combinations:
Jia-Zi, Yi-Chou, Bing-Yin, Ding-Mao, Wu-Chen, Ji-Si, Geng-Wu, Xin-Wei, Ren-Shen, Gui-You, Jia-Xu, Yi-Hai, Bing-Zi ... after 60 terms, it returns to Jia-Zi.
Not only for years, but a full time-coding system
The 60-cycle is used across four dimensions: year, month, day, and hour.
| Dimension | Description | Cycle |
|---|---|---|
| Year | A 60-year round. For example, 2024 is Jia-Chen, and 1964 is also Jia-Chen. | 60 years |
| Month | Each year starts from Yin month (lunar first month); stem-branch labels advance month by month; a full pattern completes in 5 years. | 60 months (5 years) |
| Day | Each day has one stem-branch pair; it repeats every 60 days. | 60 days |
| Hour | Each day has 12 traditional two-hour periods; paired with stems in sequence, it forms a 5-day cycle. | 60 two-hour periods (5 days) |
A full birth timestamp written in stem-branch terms is called BaZi (Eight Characters): year, month, day, and hour pillars. Example: Jia-Zi year, Bing-Yin month, Geng-Wu day, Ren-Shen hour.
Simple Analogy
If Western time uses separate units (year/month/day/hour/minute/second), the stem-branch system works like one unified gear set: the same coding logic drives year, month, day, and hour in repeating 60-step cycles.