The Ox is paired with chou, the second earthly branch, whose double-hour runs from one to three in the morning and whose phase is earth. In an agrarian society the ox was the indispensable animal, the source of ploughing power and therefore of the harvest, and the traits assigned to the sign follow directly from that: steadiness, patience, strength held in reserve, and a capacity for sustained and unglamorous work. Chinese custom protected the working ox, and there was a long-standing reluctance to eat beef in many regions for exactly that reason. In the Chinese calendar the beginning of spring was marked in some periods by the ceremonial beating of a clay spring ox, a rite performed by officials to open the agricultural year, which shows how closely the animal was bound to the calendar itself rather than merely to the list of signs.
The twelve earthly branches also alternate in polarity, yang and yin, beginning with zi the Rat as yang and running chou the Ox as yin, so that six of the twelve animals, Rat, Tiger, Dragon, Horse, Monkey and Dog, are read as yang and the remaining six, Ox, Rabbit, Snake, Goat, Rooster and Pig, as yin, a polarity distinct from and layered on top of both the five-phase element and the san he triad groupings. This yin placement is read as consistent with the Ox's traditionally receptive, patient and enduring character, in contrast to the assertive yang reputation of its triad partners the Snake and the Rooster.