When is 39 49 that people often say?

Nine cold days, also known as "Winter Nine Nine", is a folk solar term in winter in China. "Nine" starts from the "winter solstice" every year, and every nine days is a unit. March 9 and April 9 are the coldest. The coldest day. So, look at the calendar and push it yourself. The time of winter solstice is different every year.