This probably says 1941 because it’s when “all” retirees became automatically insured, but earlier or later would also be a good answer.

Otto von Bismarck instated a rudimentary system (German language link) covering only poorer workers and their families in 1883, but that expanded to cover everyone gradually and was then taken away from multiple groups in the 1930s and 1940s until it was reinstated for all in 1949.