A recent thread made me think again about timeline discrepancies in the Trilogy:

Given the nine-hours-plus length and 80-plus years’ span of the three movies, it’s not surprising that errors crept in. Some are trivial (Vito’s birthday and year of birth changing from GF to II); some are dumb (Michael’s massacre of the Dons moving backward by five years from GF to II), and some are comical (Roth is either Vito’s contemporary or his junior by 12 or 13 years, depending on which scene you watch in II). But two are troubling, and affect the credibility and logical flow of critical events:

First, some sharp-eared fans hear the radio in Sonny’s car tuned to a broadcast of the final game of the 1951 National League playoff (“The Shot Heard ‘Round the World”) as he takes his fatal drive to the causeway. As supporting evidence, they note that a “Dewey for President” poster is visible when Sonny earlier beats up Carlo. Thomas E. Dewey was the GOP Presidential candidate in 1948, and the tattered condition of the poster suggests that the scene was set in 1949 or 1950—consistent with a timeline leading to Sonny’s death on October 3, 1951.

Impossible! That’d mean that the Five Families War of 1946, with its attendant loss of life, revenues, business opportunities, political influence, etc., had been going on for almost seven years…that Sonny had survived his hot temper and lack of strategic skills for almost seven years…that Vito hadn’t risen from his sickbed (and his wounds hadn’t healed, to judge by the fresh-looking bandage on his throat) for almost seven years…that Michael had been cooling his heels in Sicily for almost seven years…and that he and Apollonia hadn’t had children (or even aged visibly) for all that time.

Second, when Michael and Kay are dancing at Anthony’s party, she says, “You said the Corleone Family would be completely legitimate in five years. That was seven years ago.” Since the party is set in late 1958, it means that Michael and Kay were married in 1951. And since Michael told Kay in GF that he’d been back in the US for “a year, maybe longer,” he must have left Sicily in 1950.

Highly unlikely! It’d mean that Michael remained in Sicily for more than four years. As Vito, Sonny, Don Tomassino (and probably Michael) knew, the danger of his being found out and betrayed would increase exponentially over time. And it would be compounded because Michael traveled around freely and insisted on having a very public wedding. And as we saw, he was found out and betrayed.

I believe that a much shorter time frame is logical and credible:

--Michael met and married Apollonia not long after arriving in Sicily in early 1946. Support: on The Day of the Thunderbolt, Michael, Calo and Fabrizio are passed by a jeep carrying American soldiers (“Take me to de America, GI!”). All US occupation troops were out of Sicily after 1946. Also, Michael visited Corleone for the first time on that day, and I infer that seeing his ancestral town would be a high priority.
--Sonny was killed in 1946. Support: FFC was very diligent about the authenticity of cars and other props in the Trilogy. The US auto industry was just gearing up postwar production in ’46, and both cars in the assassination scene are prewar: Sonny’s driving a ’41 Lincoln Continental and his killers are in a ’41 Cadillac. Also, Thomas E. Dewey was the GOP candidate in ’44 as well as ’48, so the tattered poster would be consistent with Sonny beating up Carlo (and attracting Barzini’s attention to set up the assassination) in ’46.
--Michael returned to the US in ’46, and he married Kay in ’47, or no later than ’48. Support: The clothing worn by Kay and her school kids is mid-‘40’s vintage. The only cars visible in the scene are the ’47 Cad that follows Michael, and a green ’47 Ford Super Deluxe (“woody”) wagon.

So, why the discrepancies? Michael marrying Kay in ’51 fits the 1958 plot line of II, including Anthony’s approximate age for celebrating his First Communion. But II wasn’t envisioned when GF was written and filmed. As for “The Shot Heard Round the World”: NFI. A guess: someone in the Second Unit production crew was having some fun at the expense of a colleague who’d been a Brooklyn Dodgers fan.