It is the greeting card during mid-winter from Shokan (the second coldest day) in 24 divisions of the old calendar (around January 5) to Risshun (the first day of spring) in 24 divisions of the old calendar (around February 4).
二十四節気の小寒(1月5日頃)から立春（2月4日頃）までの寒中に行う見舞いである。