What do you mean, one to nine and one to one?

entering nine means entering nine cold days.

enter, which means to enter; Nine, it is an index of nine cold days, so entering nine means: entering nine cold days.

After the "Winter Solstice" of the traditional 24 solar terms, the weather has entered the coldest stage of the year, which is often referred to as "entering the ninth". There is a folk saying that "the cold is in the third and ninth, and the heat is in the third". During the count of nine, we should pay attention to cold and warmth, especially for the elderly and children, so as not to get sick from the cold.