What are Celestial Stems and Earthly Branches?

For a moment a flaming ring was raised high up on the floor.

The ancient Yinyang principle constructed a fantastic system of 10 heavenly stems and 12 mundane branches.

The Chinese sexagenary cycle, also known as Stems-and-Branches, is a cyclic numeral system of 60 combinations of the two basic cycles, the ten Heavenly Stemsand the twelve Earthly Branches.

School with the Han Chinese and the Heavenly Stems, Earthly Branches Jinian calculation.