Since Michael came back to New York, how many years did it take for the massacre to take place?

The question you state is probably one of the top three questions that have attracted the most controversy among Board members. I've always maintained that the massacre took place in '50. Others maintain '55. I retort that it makes no sense for Michael and Vito to wait 10 years and invite the variables (among many others) of their overthrow, murders, incarcerations, or the deaths of the other Dons to intervene.

To add to what Oli said:
The visual evidence is Vito's tombstone: 1955, clearly visible. In II, the Senate subommittee chairman asks if Michael was responsible for planning the murder of the heads of the Five Families in 1950. Two movies, two dates.

But, as Oli said, Michael would have had to serve an awfully long apprenticeship under Vito. And, if their plan was to make the Corleones look weak--the better to relax their enemies--there'd be nothing left of the Corleone Family by 1955.

Go figure...

I really dont understand how the massacre could possibly have taken place in 50. First off we have Anthony who is already 3 years old, which would have made him born in 47. We know for sure that the movie starts in 45 ("this is almost 1946"). So this would mean that in less then two years Michael went to Sicily and came back, and married Kay and had a kid, which is simply not possible.

If you look at the massacre taking place in 55 on the other hand then you have a lot more breathing space. Anthony is born in 52 (or later 51) which would have been about 3 years since michael returned from Scilly (Which he came back from in 1948 because it was a few months after sonny was killed)

By using my timeline i posted above, Michael is reunited with Kay in 1950 (The 7 years comment is made in 58, but its only a year off) Michael would work for his father for about 5 or 6 years before becoming the don sometime before 55.

Well, at least that saved him from ONE count of perjury.

Also, did they go with facts or did they go with Pentangeli's sworn affidavit on the date of the massacre.

1955 might make more sense in relation to Carlo knocking up Connie, having been remiss in his husbandly duties. If Sonny is killed in 1948 then that's less than a year that Connie gets knocked up again. Certainly possible. But is it likely considering the dynamic of their relationship? Or would things get pretty cold until Michael gives Carlo a promotion?

Thanks guys

Not to mention that Anthony's first communion was in 1958.

Also keep in mind that Rocco's secret regime played a vital role in the Great Massacre. For this to work, he needed absolutely reliable men, and it more than likely would have taken years to recruit the right men and built his regime. In real life, associates are monitored for years before being admitted in the Mafia; normally this is a five years probationary period at the very least. So it's unrealistic that Rocco would have been able to built his secret regime in only two years.

In the closing chapter of The Godfather novel, Puzo specifically states that it was almost ten years after the wedding. This along with the tombstone and the latest draft of the screenplay is more than sufficient evidence that the original story ended in 1955.

Overall, and despite some of the flaws, the official timeline fits the best. I'd say just go along with this timeline and save yourself from headaches and sleepless nights...

Its only really the godfather 2 remarks that mess everything up

That's why I was thinking that the Senator was using Pentangeli's sworn (and flawed) statement rather than verified facts when asking the question.