Multiple vintage automobiles are shown during the WWII flashback scenes. Gasoline was rationed then and cars were required to display ration stickers on their windshields; none of the cars have them.
The song that the couples are dancing to at the end of the movie is Dream a Little Dream of Me being sung by Doris Day. Doris Day did not record her version of this song until 1957.
American flags shown in WWII flashback scenes were modern 50-star flags. During WWII, before the admission of Alaska and Hawaii, the American flag had only 48 stars, arranged in simple rows and columns.
Neil Thomas: When I think back about when we were growing up together I remember so many things. But for the life of me, I can't remember a time when I wasn't in love with you.