When is three nine four nine?

The so-called "Sanjiu" refers to the period from 19 to the 27th day after beginning of winter. April 9th refers to the 28th to 36th days after beginning of winter.

In other words, "Nine" is a concept of time. March 9 and April 9 are the coldest times of the year.

On the solstice after winter, there are 40 days of cold weather all year round. After beginning of winter 18 days to the day, the hands and feet are stiff, and after beginning of winter 18 days to the day-after beginning of winter 18 days to the day, it is the coldest period of the year, and the river freezes and the river is blocked; Once winter comes to 18 days from 36 days to 54 days in the future, willows along the river will sprout new buds and the climate will get warmer; From winter to the 54th day to the 63rd day, swallows fly back to the north from the south. From winter to 63-72 days in the future and beyond, the weather will be completely warm after spring ploughing.