Xushen interpreted the Ten Heavenly Stems and the TwelveEarthlyBranches as a system of the cycle of the seasons in "Shuowenjiezi".
《说文》中,许慎把“天干”、“地支”都解释为万物在一年中的萌发—生长—成熟—衰亡的循环系统。
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Heavenly Stems, EarthlyBranches and the Twelve Animal signs(shengxiaos)are brainchild of Chinese ancestors. Generally, the former are used in calculating hours while the latter numbering years.