Factual error: Another flag gaffe: The Canadian flag in the 1920s was either the red ensign or the Union Jack. The Maple Leaf only became the national flag in 1965.
Factual error: In the final football game scenes ( from about three-quarters of the way through the film or so) all the spectators are wearing 1970's clothes and have 1970's hairstyles.
Other mistake: There's no way Harry could've smashed the cigarette vending machine at the gas station without somebody inside seeing him.