Factual error: When singing "Do-Re-Mi", Maria is playing a Goya guitar. Goya brand guitars were not invented until the mid-1950s, a good ten years after this takes place.
Factual error: The story is set prior to the Anschluss, which was Austria's forced annexation with Germany in 1938. At this time Austrian vehicles still drove on the left (Hitler eventually changed that). When Von Trapp brings the Baroness to his home for the first time, he drives on the right.
Continuity mistake: During the boat scene, the baroness leaves and walks behind Maria. From the immediate opposite shot the baroness has vanished.
Factual error: When they're making their escape in the CitrĂ´en a shot is shown under the car. The tyres on the CitrĂ´en are "Michelin X" radials. These were not on the market till 1948.
Continuity mistake: When the captain sings for the first time and hugs the children, Gretl is under his left arm. In the next shot, he raises his arm and she is nowhere to be seen. Then, when Maria motions for Gretl to give the Baroness the edelweiss, she is back under his arm.
Answer: In the film, the Mother Abess explains to Maria that the Captain Von Trapp's wife died "several years" ago. This is commonly misheard by viewers as "seven years." In reality, the actual mother of the Von Trapp children was Agathe Whitehead, who died of scarlet fever in 1922, just four years before Maria came to the Von Trapp home, initially as a tutor (not a governess) in 1926.
Michael Albert