12 Earthly Branches
To keep track of days, months, and years in early Chinese civilization, a variety of timekeeping notations were used. Among these were the well-known techniques of calculating the months of the year from one to twelve and years in terms of rulers’ reigns. However, one method of timekeeping was independent of events or history, as well as natural rhythms. This was a method of counting in which two series of signs were combined, yielding a total of 60 potential possibilities. This is referred to as the “Heavenly Stems and Earthly Branches” scheme.
The original terms used for the years were actually “地支 (dì zhī) Earthly Branches”. These ‘branches’ are also assigned to the hours of the day based on solar time.
Essentially, the Twelve Earthly Branches are comprised of: 子 (zǐ), 丑 (chǒu), 寅 (yín), 卯 (mǎo), 辰 (chén), 巳 (sì), 午 (wǔ), 未 (wèi), 申 (shēn), 酉 (yǒu), 戌 (xū), 亥 (hài).