This cycle is used for keeping track of years, months, days and (double) hours in Chinese astrology. Your date and time of birth is determined by the eight characters (八字) formed by the pair of cyclical characters, or pillar, (柱, zhù), for the year, month, day and hour. The 60-day cycle has been used for keeping track of days since ancient times and go back to at least the 13th century BCE during the Shāng Dynasty (商朝, 1600--1046 BCE). The 60-month cycle is also old. The 60-year cycle was introduced during the Hàn Dynasty ((汉朝 [漢朝]) and is related to the orbital period of Jupiter. In modern times, the year cycle is the only one in common use. The branches are often associated with the sequence of 12 animals: rat, ox, tiger, rabbit, dragon, snake, horse, sheep, monkey, rooster, dog, and pig. It is not clear when the branches were associated with the 12 animals, but it seems to have taken place around the time of the Táng Dynasty.
http://www.infoplease.com/yearbyyear.html
Vote
}