The evolution of Chinese astrology dates back to at least the Zhou Dynasty (1122 BC 256 BC). Some sources claim it began as far back as 2150 BC. The ancient Chinese astrologers set about by using the position of planets, moon and stars to accurately anticipate the changing of the seasons, and flow of the tides. These forecastings were vital to the productivity of farming at the time, since they were used to anticipate the best times to plant and harvest crops.
To help them keep track of passing time, the 10 Heavenly Stems and 12 Earthly Branches were formed. These types of significant signs were used to note the passing of what we now know as hours, days, months, and years. During this period in history, only the elite astrologers could interpret and spell, so livestock were used to represent each one of the Twelve Earthly Branches.
Legend has it that during the festivity of New Year, Gautama Buddha was to decide upon the order of animals to be used for the Twelve Earthly branches. He called for all the animals in the land to join him for a meeting. Just twelve animals responded to the call of Buddha and went to the meeting.
Buddha awarded each of those twelve animals sovereignty over an Earthly Branch. Each animal was to guide the Branch and have influence over those birthed during its Branch.
We know the Twelve Earthly Branches as Years. In the conventional Chinese calendar, these twelve animal signs reduplicate themselves in a incessant circle, to remind us that time is a never ending and has flow.
The XII Earthly Branches are, in order, the mouse, ox, tiger, rabbit, dragon, snake, horse, sheep, monkey, rooster, dog, and pig.
Some ancient Chinese respected the Earth over the stars. These scientists looked for the rationalities behind the natural order of things. They concured that all things had a basis in one of Five elements. To their knowledge, all things were made from Fire, Earth, Metal, Water, or Wood.
They analyzed how these basic elements operated together and against each other. Wood creates Fire, Fire turns to Earth, Earth creates Metal, Metal creates Water, and Water creates Wood.