In the beginning of the movie, the main character (Woods) complains to his friend (Belushi) that San Francisco has become a "yuppie" town. The word "yuppie" is used frequently. However, the movie is set in 1980-81, and the term "yuppie" didn't become popular until 1983-84. An early, obscure use of the word from 1980 exists, but a syndicated 1983 magazine article is commonly viewed as the introduction of the term.
In the middle of the film, during Christmas, Cathy Moore says to Richard Boyle "you're 42 years-old." At the end of the film the border officer reports his birth date as being "2-26-43". As the story takes place during 1980-1981, Boyle would be 37 or 38 years-old during that time period.