Factual error: When Chitty Chitty Bang Bang arrives at the Potts' house, Grandpa Potts is sitting in a deckchair reading a very modern colour edition of National Geographic magazine.
Factual error: Rosemary calls Dr. Hill from a pay phone and says, "The baby's due on Tuesday, you remember you told me June 28th" (and June 28th 1966 does fall on a Tuesday). In the previous scene in Dr. Sapirstein's office his receptionist is making an appointment "next week" for a patient and that date is "July 10th" indicating that if Rosemary is due on June 28th (which she says is next Tuesday) the dates do not match and it must still be the week of June 20th which is at least two weeks before July 10th. (01:44:45)