Twenty-eight Lunar Mansions
Divide the stars near the celestial equator into twenty-eight groups, with one mansion taking duty each day. They are grouped into four images: Azure Dragon of the East, Black Tortoise of the North, White Tiger of the West, and Vermilion Bird of the South, each with seven mansions, each assigned one of the Seven Luminaries (Sun, Moon, and five planets) and an animal.
The Twenty-eight Lunar Mansions (èr shí bā xiù) are twenty-eight star regions defined by ancient Chinese astronomy, dividing the stars near the celestial equator and taking duty in daily sequence. These twenty-eight mansions are equally distributed among the four great celestial images: Azure Dragon of the East, Black Tortoise of the North, White Tiger of the West, and Vermilion Bird of the South, with each image containing seven mansions. Each mansion corresponds to one of the Seven Luminaries (Sun, Moon, Venus, Jupiter, Mercury, Mars, Saturn) and an animal. In traditional date selection, the auspicious or inauspicious nature of the Twenty-eight Lunar Mansions is one of the reference criteria for judging the quality of a day.