When Sam hides his father John's cigarettes, his mother suggests to John that he's smoked his carton already. John remarks that a carton always lasts until Friday, and that it's only Tuesday. However, Sam leaped back to November 25, 1969, which was a Tuesday. The cigarette scene was the second day of his leap, 11/26/69, a Wednesday.
"Post Raisin Bran" cereal box on kitchen table is from 1990, not 1969.