Predicting the future by observing the stars and planets was an ancient art long before Europeans discovered/invented the mathematics necessary to make these same predictions. However, the yearly Animal signs bear the much same relationship to Chinese Astrology as Sun Signs have to Western Astrology - a cursory overview, and over simplification. As with Western Sun Signs, the twelve Animals of the Chinese zodiac do represent archetypes useful to writers.
Find Your (or Your Character's) Animal Sign
Some books on the subject: Chinese Astrology