How did the vernal equinox, summer solstice, autumn equinox and winter solstice come about?

When Yao, the ancestor of humanity, was in office, he was observant, decisive, clear-minded, far-sighted, well-run and resourceful. Yao ordered the minister and his family to carefully calculate the movement laws of the sun, the moon and the stars according to the number of days, make a calendar and tell people about the weather and festivals.

Under Yao's arrangement, the minister lived in Tanggu in the east and greeted the sunrise respectfully every day to determine and measure the time when the sun rose every day. When the length of day and night is equal, the southern rosefinch appears in the south of the sky at dusk on seven nights. Xi Zhong designated this day as the vernal equinox. At this time, people scattered in the fields to work and farm, and birds and animals began to breed at this time.

Under Yao's arrangement, the minister's uncle lives in the south and greets the sun moving southward respectfully every day to determine and measure the situation of the sun moving southward every day. In Seven Nights of the Oriental Black Dragon, when the day is long and Mars appears in the south at dusk, Uncle Xi designated this day as the summer solstice. At this time, people began to move to high places to live, and the feathers of birds and animals began to become sparse at this time.

Under Yao's arrangement, the minister and Zhong lived in the valley of ignorance in the west, and respectfully bid farewell to the sunset every day to identify the time when the sun set in the west. When the length of day and night is equal, and the virtual star in the seven nights of Xuanwu in the north appears in the south of the sky at dusk, the clock will set this day as the autumnal equinox. At this time, people moved back to the flat land from high places to live, and at this time, birds and animals began to regenerate new hair.

Under Yao's arrangement, the minister and uncle lived in a secluded capital in the north and watched the movement of the sun northward every day. When the days became shorter and the Pleiades of the West White Tiger appeared due south at dusk, Uncle He designated this day as the winter solstice. At this time, people began to live indoors, and birds and animals began to grow soft fine hair.