While discussing changes for the CBS prime-time schedule, Bill Paley states he'd rather leave Dragnet where it is. There's just one problem: Dragnet aired on NBC.
While at a dinner party in 1955 Jamaica, Truman spills the details of an upcoming novel about a New York Society murder and suggests Bill Paley (CBS President) run it by his "60 Minutes" Producers. "60 Minutes" did not air until 1968, over a decade after the dinner party at Montego Bay took place.
While recounting her return from Paris in 1968, Babe Paley "stepping off Concorde". The BAC/Aerospatiale Concorde's first test flight was in 1969 and eventually went into scheduled service to the USA in 1977.
During the dinner flashback scene, in Jamaica, set in 1955; Capote references the news program "60 Minutes" to Bill Paley, President of CBS. The show did not premiere until 1968.
The opening scenes are set in 1968 yet Babe Paley casually mentions just getting off the Concorde from Paris. But the Concorde's first flight wasn't until 1969, and transatlantic service didn't begin until 1977.