Chinese festivals are often based on lunar cycles, which brings about the months in Chinese calendars. Each month is equivalent to one lunar cycle, about 29.5 days. This is slower in comparison with the solar calendar, which has about 30 days each month. Hence, in order to 'catch up' with the solar calendar, the Chinese calendars have leap years - once every seven years. In leap years, an extra month is inserted, the month depending on other forms of calculations (for example, the lunar calendar in 2006 has an added seventh month, called the run qi yue '闰七月').
On top of the months, the Chinese also have a zodiac system of 12 animals: Rat, Ox, Tiger, Rabbit, Dragon, Snake, Horse, Sheep, Monkey, Rooster, Dog, Boar. Apparently, the Buddha once summoned all living creatures to come before him, but only these twelve came at his bidding, in this particular order. Hence he bestowed upon them the honour of having a year named after them.