What are the nine days often mentioned in customs?

"Winter solstice days and 998 1 day are cold." Counting nine cold days means 8 1 day from winter solstice to "999", and counting nine every nine days.

99. China folk method for calculating the date of cold weather and warm spring in bloom. 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.

The number nine method is passed down from mouth to mouth among the people in our country, which has a history and lacks records. As for when it originated, there is no exact information. In traditional culture, nine is the extreme number, the "highest yang" number and the largest number. The accumulation of "Zhiyang" means that Yin Qi is decreasing day by day, and it is tired to the end, which means that the cold is getting warmer and "the spring is deep".

Extended data:

The method of calculating cold and warm by number nine is suitable for areas where the temperature changes obviously from winter to around in China. The calculation of temperature and warmth changes is accurate to days. Judging from the number of days from winter to Sunday, the coldest periods are "March 9 and April 9", while counting to "998 1 day" is a warm day in late spring.

There are also some places that count to nine from the day of winter solstice. In some cold areas, the temperature in winter and spring is below zero degrees Celsius for a long time in the ice and snow, and the temperature change is not obvious from winter to around. "Nine days" is not much different from the temperature. For the convenience of counting nine, counting begins from the date of winter solstice, that is, the date of winter solstice is called "cross nine", every nine days is "nine nine", and so on.