The Chinese calendar follows a 12-year pattern, the Zodiac, with each year named for an animal. There are many legends about how the animals were chosen for the Zodiac. One of the more popular legends is this:
Long ago, the Jade Emperor, who ruled the Heavens, wanted 12 animals to represent the 12 calendar years. So he invited all animals to a swimming race. The first 12 animals to cross the river would appear on the Zodiac in the order they finished the race.
At that time, the Cat and the Rat were very good friends and planned to go to the race together. The day came and the Cat decided to have a nap so that he could be in good form. He asked his friend: "Could you please wake me up when it's time for the race?"
"Have a good nap. I will wake you up," said the Rat. But when the time came, the Rat wanted to win so badly, he left the Cat sleeping and went alone.
In the race, the Ox, the best swimmer, took the lead. When the Ox was near the end, the sly Rat jumped on the Ox's head and then right onto the riverbank to finish first!
The Jade Emperor was very pleased and named the first year of the Zodiac after the Rat. The second year of the Zodiac was named after the Ox. The Tiger, Rabbit, Dragon, Snake, Horse, Goat, Monkey, Rooster, Dog and Pig followed and found their places on the calendar.
When the Cat found out what the Rat had done, he was very angry. The two became enemies. Because of the Rat, the Cat is not one of the twelve animals of the Zodiac. It is why cats have chased rats ever since!