Why are Chinese calendars based on animals?

A large percentage of the Chinese are followers of Taoism. According to Taoist belief, the Jade Emperor is the ruler of heaven, mankind and hell. It is said that the Jade Emperor decided to assign a different animal for each year, so that people could easily remember the twelve-year zodiac cycle. So he called one representative from each animal species and held an obstacle race for them. The first 12 animals were selected.

Each of the 12 animals are governed by an element plus a Yin Yang Direction.

1. Rat (Yang, 1st Trine, Fixed Element Water).
2. Ox (Water buffalo in Vietnam), (Yin, 2nd Trine, Fixed Element Water).
3. Tiger (Yang, 3rd Trine, Fixed Element Wood).
4. Rabbit (Cat in Vietnam) (Yin, 4th Trine, Fixed Element Wood).
5. Dragon (Snail in Kazakhstan) (Yang, 1st Trine, Fixed Element Wood).
6. Snake (Yin, 2nd Trine, Fixed Element Fire).
7. Horse (Yang, 3rd Trine, Fixed Element Fire).
8. Ram (Goat in Vietnam) (Yin, 4th Trine, Fixed Element Fire).
9. Monkey (Yang, 1st Trine, Fixed Element Metal).
10. Rooster (Yin, 2nd Trine, Fixed Element Metal).
11. Dog (Yang, 3rd Trine, Fixed Element Metal).
12. Pig (Boar in Japan) (Yin, 4th Trine, Fixed Element Water).