He ordered Xi Zhong, who lives in Tanggu in the east, to greet the sunrise respectfully and set the time for the sun to rise. The length of day and night is equal, and the southern rosefinch appears in the south of the sky at dusk for seven nights, which is designated as the "vernal equinox".
He ordered Uncle Xi, who lives in the south, to identify and measure the movement of the sun to the south, and respectfully welcomed the sun back to the south. The day is the longest, and Mars in the Seven Nights of the Oriental Black Dragon appears in the south at dusk, which is designated as "summer solstice".
Command and Zhong, living in the valley of ignorance in the west, respectfully bid farewell to the sunset, identify and measure the time when the sun sets in the west, and the length of day and night is equal. The virtual stars in the seven nights of Xuanwu in the north appear in the south of the sky at dusk, and this day is designated as the "autumn equinox".
Command and uncle, living in the secluded capital of the north, observe the movement of the sun to the north. The day is the shortest, and the Pleiades star of the West White Tiger with seven nights appears in the south at dusk, which is designated as "winter solstice".
After the order was issued, Emperor Yao taught them: The first anniversary of your family and He family is 366 days. You should determine the age of the four seasons by adding leap months. So the responsibilities of officials were defined, and all kinds of things came into being.