Excellent find. This would make Michael's return 1949 like I initially believed.

But considering all the facts, arguments and inconsistenties I've already made my conclusions.

Mike flees to Sicily in January 1946. Vito returns home in late March 1946 (newspaper article states he was in the hospital for twelve weeks). Sonny is killed in August or September 1946. Michael returns in September 1947. Michael reunites with Kay in Oktober 1948 (In the film it was Autumn and he was back for more than a year).