What does it mean to "enter nine" in winter? What is the coldest day?

The number "Nine" in the lunar calendar is a miscellaneous festival used in China. When you enter the winter solstice, count to nine, which is what people call "Winter Count Nine". It starts from the winter solstice. Nine days is September 19, nine days is February 29 ... Counting September 9 is the end of September 9, and it will be warm then. March 9 and April 9 are the coldest seasons of the year.

According to the provisions of the almanac, "counting from the third Geng day in summer", that is to say, counting down from the summer day and crouching from the third Geng day. The "Geng Day" here refers to the days prefixed with "Geng" in the ancient "Ganzhi Jiri Law". It is also stipulated in the Almanac that the first Geng Day after the "beginning of autumn" solar term is the day when the last volt begins.

People say that "the cold is in nine, and the heat is in the volt." Although the number nine is cold, it is different because of China's vast territory:

The "Jiujiu Song" in the middle and lower reaches of the Yellow River is: 1929 without a gun; Walking on the 3949 River; 5969 see willows along the river; Seven or nine talks, eight or nine geese come; 1999 and 1999, cattle are being farmed everywhere.

Jiangnan's "Jiujiu Song" is: 1929, meeting a husband; On March 27th, cymbals (an ancient musical instrument, meaning the fence crackled with cold wind) were played at the fence head. 4936, the night is like a heron (the cold night is like a crane sleeping); In 5945, the sun opened the door, and in 6954, poor children fought for spirit; In 7963, cloth sleeves were worn on the head; In 8972, the cat looked for the sun; Plow and rake go out together.

The "Jiujiu Song" in North China is: 1929, water does not flow; 3949 ice-breaking stone mortar; In 5945, birds danced in the sky; 6954, the fence has tender thorns; 7963, go out and take off your clothes; In 8972, the yellow dog was lying in the shade; 998 1, plow cattle together.