Tai Sui

Tai Sui is a Chinese astral deity connected with the planet Jupiter and, more precisely, with an invisible counter-Jupiter used to reckon the twelve-year cycle, and, by extension, with the sixty gods of the sexagenary cycle, each of whom governs one year in turn. In popular belief Tai Sui, the Grand Duke of the Year, presides over the fortunes of the year, and it was held dangerous to offend him, for instance by digging or building in the direction he was thought to occupy. Those whose birth-sign clashes with the ruling Tai Sui of a given year are traditionally reckoned to be in for an unlucky year, and perform rites or make offerings at temples of the sixty Tai Sui to appease him and avert misfortune, a practice, sometimes called an Taisui, that remains common in the Chinese world and at Daoist and folk temples. The system ties the reckoning of time to the everyday management of luck, and Tai Sui devotions are among the more frequently observed of popular ritual customs.

Tai Sui's origin lies in a practical problem of ancient Chinese astronomy rather than in myth. Jupiter's real orbital period is close to, but not exactly, twelve years, roughly eleven point eight six years, so a calendar that tried to track the twelve Earthly Branches directly against the planet's actual position in the sky would slowly drift out of alignment over the centuries.

Chinese astronomers of the Warring States and Han periods solved this by inventing a fictitious counter-Jupiter, a hypothetical body imagined to move steadily through the twelve positions in exactly twelve years, moving in the opposite direction to the real planet across the sky, so that its position could be calculated cleanly and used to name years according to a fixed, drift-free cycle. This calculated, invisible body was Tai Sui, an astronomical convenience before it became, in later centuries, an object of religious dread and propitiation in its own right. Around this originally technical device, popular religion built the belief, still widely observed, in one's benming nian, one's own zodiac year recurring every twelve years, understood as a year of heightened vulnerability when a person's fate stands in especially close, and potentially dangerous, relation to the ruling Tai Sui; the common folk remedy is to wear something red, traditionally a red belt, red underwear or a red string bracelet, throughout that year to ward off the associated bad luck. What began as a mathematical fix for tracking Jupiter's calendar thus ended as one of the most widely and personally observed pieces of living Chinese folk religion, followed today by many who have never heard of the astronomical problem that gave the god his name.