10 Heavenly Stems and 12 Earthly Branches

Heavenly Stems & Earthly Branches originated from the observation of astronomical phenomena in ancient China. 10 Heavenly Stems are Jia (甲), Yi (乙), Bing (丙), Ding (丁), Wu (戊), Ji (己), Geng (庚), Xin (辛), Ren (壬) and Gui (癸). 12 Earthly Branches are Zi (子), Chou (丑), Yin (寅) , Mao (卯), Chen (辰), Si (巳), Wu (午), Wei (未), Shen (申), You (酉), Xu (戌) and Hai (亥).

Zi-Rat, Chou-Tiger, Yin-Tiger, Chen-Dragon, Si-Snake, Wu-Hose, Wei-Goat, Shen-Monkey, You-Rooster, Xu-Dog, Hai-Pig

Heavenly Stems Jia, Bing, Wu, Geng, Ren belong to Yang.
Earthly Branches Zi, Yin, Chen, Wu, Shen, Xu belong to Yang.
They all have meanings of increase, prosperousness and strength.

Heavenly Stems Yi, Ding, Ji, Xin, Gui belong to Yin.
Earthly Branches Chou, Mao, Si, Wei, You, Hai belong to Yin.
They have meanings of decrease, decline and shrink.

Jia and Yi belong to Wood element. Jia is Yang Wood and Yi is Yin Wood;
Bing and Ding belong to Fire Element. Bing is Yang Fire and Ding is Yin Fire;
Wu and Ji belong to Earth Element. Wu is Yang Earth and Ji is Yin Earth;
Geng and Xin belong to Metal Element. Geng is Yang Metal and Yin is Yin Metal.
Ren and Gui belong to Water Element. Ren is Yang Water and Gui is Yin Water.

Yin and Mao belong to Wood element. Yin is Yang Wood and Mao is Yin Wood;
Si and Wu belong to Fire Element. Si is Yang Fire and Wu is Yin Fire;
Shen and You belong to Metal Element. Shen is Yang Metal and You is Yin Metal.
Zi and Hai belong to Water Element. Zi is Yang Water and Hai is Yin Water.
Chen, Xu, Chou and Wei belong to Earth Element. Chen and Xu are Yang Earth. Chou and Wei are Yin Earth.

Combination Rules: Yang Heavenly Stems Match with Yang Earthly Branches. Yin Heavenly Stems Match with Yin Earthly Branches.

The ten heavenly stems and the twelve earthly branches combine with one another and form 60 basic cycles in a fixed pattern, which is called the stem-branch calendar. The invention of heavenly stems and earthly branches has a far-reaching influence. So far, Heavenly Stems and Earthly Branches are still widely used in China for calendar, astrology, calculation, naming and other aspects.