In the Shang, time was represented by a system of combining shi gan (ten stem signs) and shi-er zhi (twelve branch signs), a complete cycle taking sixty days.

Many interpretations, some dating back to the Han period, have been made as to the meaning of the signs. I question the suitability of these theories and, using the original meaning of the characters together with different words of similar sound propose the possibility of a systematic interpretation. Shi gan symbolize stages in the development of a barley seed from germination in the earth to fruition, while shi-er zhi are taken to be stages from the conception of a child up to acceptance into the family. The cycle of the two sets of signs represents the idea of the diffusion of two forces within the cosmos: that which gives life to plants and all living things and that which gives them form and substance. Attention is also drawn to the relationship of the former with sun-worship and to that of the latter with moon-worship.