Chinese Zodiac Calculator

The twelve animal signs are the visible face of the sexagenary cycle, or ganzhi, a Chinese calendrical count pairing ten heavenly stems with twelve earthly branches. Because 10 and 12 have a lowest common multiple of 60, the pairs repeat every 60 years, and only 60 of the 120 conceivable combinations ever occur, since stems and branches advance together and so keep the same parity. Each branch carries one animal, Rat through Pig; each pair of consecutive stems carries one of the five phases, wood, fire, earth, metal, and water; and the alternation of stems makes odd years yin and even years yang. The arithmetic here, animal from year minus 4 modulo 12 and phase from year minus 4 modulo 10, works because the year 4 CE is reckoned as a jia-zi year, the first position of a cycle, which is why 1984 and 2044 repeat it exactly. The main caveat is the boundary. The animal changes at Chinese New Year, the second new moon after the winter solstice, which falls between January 21 and February 20, so anyone born in January or early February belongs to the previous animal despite what a Gregorian-year shortcut reports. Traditional Bazi or four pillars astrology uses a different boundary again, the solar term Lichun around February 4. Assignments of lucky numbers, colors, and compatible animals are folk convention that varies between regional sources and rests on story and wordplay rather than on any derivation: the Rat and Ox pairing, for instance, comes from the folk tale of the Great Race. None of it carries predictive standing.

The stems and branches are among the oldest continuously used counting systems in the world. Shang dynasty oracle bone inscriptions from around 1200 BCE already record days in a 60-unit ganzhi cycle, and the same cycle was later extended from days to years, becoming the standard way of dating years during the Han dynasty and after. The branches were originally abstract calendrical markers with no animals attached; stems and branches began life as a way to number days, not to describe character. Animal associations appear later. Bamboo slips excavated at Shuihudi in Hubei in 1975, dating from the third century BCE, contain a divination text listing animals paired with branches, close to but not identical with the modern set, and the philosopher Wang Chong gives correspondences in his first century CE work Lunheng. From China the system passed to Korea, Japan, Vietnam, Mongolia, and Tibet, picking up local substitutions on the way: Vietnamese tradition uses the cat rather than the rabbit and the water buffalo for the ox, and the Thai and Tibetan cycles differ in places as well. Five phase theory, wu xing, developed as a separate cosmological scheme during the Warring States and early Han periods and was later merged with the stem and branch count, which is what produces the sixty-year grand cycle still used for everything from dynastic chronology to naming a year such as the jia-chen wood dragon year of 2024.