People often say that the number of nine days starts from which solar term?

"Nine" started from the second day of "Winter Solstice" in late February and early February of Gregorian calendar 65438.

Counting nine is China's traditional way of recording time. Every nine days from winter, the solstice is nine days, and * * * is nine days. Usually, the first three or nine days of counting nine, that is, winter to the first month in the future, is the coldest day of the year, so there is also the saying of "three or nine winters" or "counting nine winters".