Archeological discoveries show that ancient people in China began to use the Celestial Stem and the Terrestrial Branch to record time as early as the Yin and Shang period about 4,000 years ago.

Within each 60-year cycle, each year is assigned name consisting of two components:

The first component is a Celestial Stem. These words are Jia, Yi, Bing, Ding, Wu, Ji, Geng, Xin, Ren, Gui in Pingyin and they have no English equivalents.

The second component is a Terrestrial Branch. The names of the corresponding animals in the zodiac cycle of 12 animals are given in parentheses. They are Zi (rat), Chou (ox), Yin (tiger), Mao (hare, rabbit), Chen (dragon), Si (snake), Wei (sheep), Shen (monkey), You (rooster), Xu (dog) and Hai (pig).

Each of the two components is used sequentially. Thus, the 1st year of the 60-year cycle becomes Jia-Zi, the 2nd year is Yi-Chou, the 3rd year is Bing-Yin, etc. When we reach the end of a component, we start from the beginning: The 10th year is Gui-You, the 11th year is Jia-Xu (restarting the Celestial Stem), the 12th year is Yi-Hai, and the 13th year is Bing-Zi (restarting the Terrestrial Branch). Finally, the 60th year becomes Gui-Hai.

This way of naming years within a 60-year cycle goes back approximately 2000 years. A similar naming of days and months has fallen into disuse, but the date name is still listed in calendars.

It is customary to number the 60-year cycles since 2637 B.C.E., when the calendar was supposedly invented. In that year the first 60-year cycle started.