The king of the earth is the first three days of that festival.

King Tu is not the first three days of a festival, but the first nine days and the last nine days of March, June, September and December.

In ancient times, a year was divided into four seasons, namely, spring, summer, autumn and winter, and eight seasons, namely, beginning of spring, Changxia, beginning of autumn, beginning of winter, vernal equinox, autumnal equinox, summer solstice and winter solstice. Later, the first solar term of each month is called solar term, and qi means neutral qi. The second solar term of each month happens to be the time when the sun crosses the palace to exchange gas, so it is called gas.

This month is the time of gas exchange, that is, the five elements are at their peak, so Tuwang 18th is the first nine days and the last nine days of gas in March, June, September and December.

March contains the atmosphere of Tomb-Sweeping Day and Grain Rain, so the first nine days and the last nine days and the eighteenth day of Grain Rain are the days when the soil is rich in spring. June includes the light summer festival and the great summer heat, so the first nine days, the last nine days and the eighteenth day of the great summer heat are the most prosperous days in summer.

September is the cold dew festival, and the first frost is full of breath, so the ninth day and the last nine or eighteen days of the first frost are the most prosperous autumn festival. December is a slight cold festival, which is very cold, so the first nine days, the last nine days and the eighteenth day of the great cold are when winter is booming.

Extended data:

In many places, when the soil is prosperous, it is generally not necessary to break ground. Some people should avoid "soil flourishing" when they borrow soil from the mud stove door, which is called "soil flourishing for use" in the almanac.

This statement is just a legendary way of externalization, which is convenient for everyone to remember. Then, in the operation and change of life, I realized that if the relationship between heaven and man is regarded as superstition, it will inevitably go with the flow, which is in line with the traditional intention, and the prosperity of the earth actually has deep significance.

That is the theory of image, which discusses the corresponding changes of qi and blood in the four seasons. Soil is the focus of the spleen and stomach, and soil is prosperous in all seasons. The "earth flourishing" of the four seasons reasonably explains the law of the interaction between heaven and earth and qi.

Baidu Encyclopedia-Tuwang