The Vietnamese zodiac is used to calculate the lunar year. It comprises 12 zodiac animals arranged according to a fixed order: Rat, Buffalo, Tiger, Cat, Dragon, Snake, Horse, Goat, Monkey, Rooster, Dog, and Pig. Each Vietnamese zodiac animal corresponds to 12 hours in one day and 12 months in another year. Also, the ancient Vietnamese created a concept of "giáp" which means twelve-year cycle.