The Chinese animal signs-- Animal Zodiac

The Chinese animal signs are a 12-year cycle used for dating the years. They represent a cyclical concept of time, rather than the Western linear concept of time. Every year is assigned an animal name or "sign" according to a repeating cycle: Rat, Ox, Tiger, Rabbit, Dragon, Snake, Horse, Sheep, Monkey, Rooster, Dog, and Boar. Therefore, every twelve years the same animal name or "sign" would reappear.
According to Chinese legend, the twelve animals quarreled one day as to who was to head the cycle of years. So they held a contest: whoever was to reach the opposite bank of the river would be first and the rest of the animals would receive their years according to their finish. All the twelve animals gathered at the river bank and jumped in. Unknown to the ox, the rat had jumped upon his back. By jumping off the ox's back, the rat won the race and became the first year of the animal cycle.
The animal signs also serve a useful social function for finding out people’s ages. Instead of asking directly how old a person is, people often ask what his or her animal sign is.