There is a folk saying in our country called "99", which is used to calculate the seasons. The calculation method is that every nine days from the winter solstice is a "nine", the first nine days are called "nine", the last nine days are called "two nine", and so on, until the ninth nine days, until the number of days is 998 1. At this time, winter has ended and spring has arrived.
According to the practice of previous years, the temperature is the lowest in the whole year. There is a proverb: "1929 don't shoot, walk on the ice in 3949, watch the willows along the river in 5969, open the river in 79, the geese come in 89, and plow cattle everywhere in 99." Is the characteristic of three or nine days. When the temperature is low for three or nine days or four or nine days, frozen soil will appear.
Extended data:
Production mechanism of loose wine
The coldest period in winter usually occurs after the winter solstice. After beginning of winter, it means that it has entered winter, but it doesn't mean that it has started to get cold. So the heat stored on the surface in the second half of the year still has some energy, so it is not very cold. There is a folk saying that it is "a spring in October". "Xiaoyangchun in October" refers to the sunny, warm and comfortable "Xiaoyangchun" weather in Mengdong, so in fact, early winter (Mengdong) is generally not very cold.
But with the passage of time, cold air frequently goes south, and the temperature gradually drops. In winter, the so-called "cold on March 9 and April 9" is usually not too cold before the winter solstice, but the real cold is after the winter solstice, especially on March 9 and April 9.