The date is based on which of the twelve gods, the star god on duty and the twenty-eight stars.

These 28 stars are: Jiaomujiao, Kang Jinlong, Nyctereute, Fangri Rabbit, Xinyue Fox, Tail Fire Tiger, Jishui Leopard, Muan Jing, Ghost Golden Sheep, Liutu Zhang, Xingri Horse, Zhang Yuelu, Winged Fire Snake, Lumbricus, Kuimu Wolf, Loujin Dog, Stomach Pheasant and so on.

Twenty-eight stars were originally used by the ancients to observe the movements of the sun, the moon and the five stars. They can be used as signs to explain the moving positions of the sun, the moon and the five stars, but now they are used in the yellow calendar to infer the good or bad days.

Some stars have certain rules to follow. For example, the changes of some stars are closely related to the changes of seasons and meteorology, and the occurrence of floods and droughts and the abundance and sorrow of agriculture are also inferred from this, which includes certain astronomical meteorology and agricultural science. This prediction can be further studied. Among them, the predictions related to political goodness are mostly hypothetical. There seem to be some rules for astrologers to judge the good luck and bad luck of each royal residence. The rule is to name stars according to their shape, size, brightness or color, and then make corresponding judgments according to these. For example, Petunia and Weaver Girl are named after stars. Since then, most of their good luck or bad luck has been related to cows, fabrics and women. For example, "The Battle of the Yellow Emperor" said: Petunia died and Daniel died; The little star died, and the calf died of an epidemic. The Weaver Girl is the magnificent mansion of the main silk. Samsung brightens up, the world is peaceful, and silk is cheap: the stars are unknown, and there are worries behind the main silk, and silk is expensive. The shape of a star can be associated with different things, so the same star can have different views. For example, morning glory can also be imagined as a river drum (also known as a heavenly drum). Since it is a river drum, it is related to the military. "The Battle of the Yellow Emperor" says that the general will be the general, and the left and right will be the left and right generals. Therefore, he is considered to be related to the good or bad of military and political events.