The Chinese lunar calendar dates back to the second millennium BC. Unlike our calendar, which numbers the years progressively from a given time (the birth of Christ), the Chinese calendar is cyclical. Each cycle is made up of 12 years; after the 12th year, the cycle is repeated. The Chinese associate each year of a 12-year cycle with an animal, and they refer to the years as "the year of the dragon," "the year of the ox," and so forth. The 12 animals and the years associated with them are often represented on a circular chart, and for this reason they are known as animals of the zodiac. care of "trying to sound intelligent" wikipedia again