What does 29 days mean?

The meaning of 29 days: from the tenth day to the eighteenth day of the winter solstice.

Generally, March and April are the coldest time, which is the coldest time of the year. When you count to nine "nine days" (998 1 day), spring will be deep and warm, and everything will be full of vitality. It's time for spring ploughing.

There is a folk proverb: "Don't do it on September 19th and 29th. Jiujiu, also known as Winter Jiujiu, is a folk solar term in China. The number nine started from the end of 65438+February in the Gregorian calendar, and was popular in the Southern and Northern Dynasties from the beginning of early winter to the wedding day.

Generation mechanism:

During the winter solstice, the daytime is the shortest, the angle of direct sunlight on the ground is the smallest, and the sunshine intensity per unit area on the ground is also the smallest, so the ground gets the least solar heat every day, and the daily heat budget deficit on the ground has not reached the maximum.

On the solstice after winter, although the day is growing day by day, the growth rate is very slow. From the winter solstice to the "March 9th" period, the average daily growth rate is only about one minute, and the direct angle between the sun and the ground is slowly increasing. The daily heat budget of the ground is still in a deficit state, so it continues to lose heat and the ground temperature continues to drop.

The deficit of total heat budget on the ground only reached the maximum in April and September, and the temperature was mainly affected by the ground temperature, resulting in the lowest temperature in March and April. In addition, around March 9, the cold air mass in Siberia also developed to a very strong stage, and the frequent invasion of strong cold air is also one of the reasons for the low temperature.

Refer to the above? Baidu Encyclopedia-Count Nine