I have the e-book version of the novel and can look up every detail. I will citate the beginning of chapter 19 in which Sonny is killed.

"Perhaps it was the stalemate that made Sonny Corleone embark on the bloody course of attrition that ended in his own death. Perhaps it was his dark violent nature given full rein. In any case, that spring and summer he mounted senseless raids on enemy auxiliaries ..."

And 1948 can be found in chapter 22 which is about Lucy Mancini and Jules Segal.

But I think you're probably right now, as I just saw that the same chapter begins with that it's "one year after Sonny's death".

So this makes Sonny's death in 1947, and that means Michael returns home in 1948. This completely fits with his "two year exile".

Case solved! smile

But then again, this is the timeline of the novel. In the film Michael returns home in 1950, cause this is supposedly mentioned in the original script, or Coppola's own personal notes.

Proof for this can be found in the book "The Annotated Godfather - the complete screenplay" by Jenny M. Jones.

And in The Sicilian, Michael also returns home in 1950.

"It was between the brothers Kay -- I had nothing to do with it."