Chinese sexagenary cycle

[NZBC]

en.wikipedia.org/wiki/Sexagenary_cycle#Sexagenary_Cycle

The Chinese sexagenary cycle (Chinese: ¸ÉÖ§; pinyin: g¨¡nzh¨©) is a cyclic numeral system of 60 combinations of the two basic cycles, the ten Heavenly Stems (Ìì¸É; ti¨¡ng¨¡n) and the twelve Earthly Branches (µØÖ§; d¨¬zh¨©). These have been traditionally used as a means of numbering days and years, not only in China but also in other East Asian nations like Japan, Korea, and Vietnam. It is also an important part of Chinese astrology.

[NZBC]

In a traditional story of the twelve animals, the cat and rat were once good friends, but the animals to be selected to represent the years included the rat but not the cat. These animals had to present themselves to be given the honour of representing the years in the cycle, and the cat asked the rat to wake him up before they had to go. The rat didn't do this, but instead went himself. When they came to cross a river, the rat jumped on the ox's back, and just before the ox got to the bank, the rat jumped off and was first in line. This is why the twelve animals are lead by the rat, and because the cat was cheated out of its rightful place, rats are forever sought out by cats for revenge.