The Chinese cyclical system begins to be used for reckoning years as well as days in the early years of the first century CE. (The Chinese year, which consists of twelve lunar months, will from time to time adjusted to the solar year by the addition of an intercalary month.)

During the Han dynasty, each branch had been matched with an animal name, producing the series: rat, ox, tiger, hare, dragon, serpent, horse, sheep, monkey, cock, dog, and pig.

The Chinese year begins with the second new moon after the winter solstice, which occurs between January 21 and February 19.

In 13, under Emperor Wang Mang's rule, the Celestial or Heavenly Stems, a Chinese system of ordinals that first appear around 1250 BCE during the Shang dynasty as the names of the ten days of the week, are incorporated to number the years and replace the previous system, which used only the Earthly Branches, a similar cycle of twelve days.