It's impossble to derive an accurate timeline from the films--too many inconsistencies. I did one based on the novel, but that's a different story because the novel didn't include the post-1955 Part II material.

Don't be misled by the Dewey for President poster in the scene where Sonny beats up Carlo. Dewey ran for president in 1944 as well. That could put the beating in 1946, which is where I think it belongs.