The Chinese animal signs are a 12-year cycle used for dating the years.
In the Chinese calendar, the beginning of the year falls somewhere between late January and early February.The Chinese have adopted the Western calendar since 1911, but the lunar calendar is still used for festive occasions such as the Chinese New Year. the Jade Emperor invited all the animals in creation to a race, only twelve showed up: the Rat, Ox, Tiger, Rabbit, Dragon, Snake, Horse, Lamb, Monkey, Rooster, Dog, and Pig, and according to their places in the race, the Jade Emperor had given them each a number starting with the Rat who was the winner of the race.Many Chinese calendars will print both the solar dates and the Chinese lunar dates. Many legends arose from the Race of the Chinese Zodiacs. The rat stayed on top of the ox's head until the ox was almost at the finish line.One told of the reason why cats and rats shall always be enemies: He and the cat (at the time good friends) were poor swimmers, so they asked the ox if they could stay on top of his head to cross the river. And as the ox was about to cross it, the rat jumped from the ox's head and became first place. Another legend tells that the cat had asked the rat to wake him up the day of the Race.The rat agreed, but on the said day, he did not wake the cat in his greed to win.When the cat finally woke up and got to the racing ground, he found the race to be over. The legend of the Zodiac Race, of course, is by far the least credible of all explanations of the origin of the Chinese zodiac.
Because the "Twelve earthly branches" which correspond with the zodiac, was already in existence as early as the era, long before the advent of Buddhism.
A parallel decimal set of symbols called "Ten heavenly stems", corresponding with "Yin-yang" dualism and the "Five elements (Chinese philosophy)" (wood, fire, earth, metal, water) was in existence in the "Shang dynasty" as the stems were part of Shang rulers' names.
The order of 12 Chinese zodiac animals was based on the number of toes/hooves, alternating between even and odd numbers.
Rat was the first because unlike other animals of the Chinese zodiac which all had the same number of toes/hooves on each leg, rat has four toes on the front legs and five on the rear legs, so it was selected to be number one.
Ox is second with four hooves on each leg, and tiger is the third three with five toes, hare is the fourth with four toes, dragon is next in line with five fingers on its claw, while snake ranks number six because it lacked any legs and zero is an even number, etc.
The Zodiac, or the twelve earthly branches, is probably devised together with the ten heavenly stems.