Division of solar terms of the earth king

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.