While in Vietnam, the main character and others are seen wearing the subdued 101st Airborne division patch, which had not yet been designed and was not allowed for wear until nearly 20 years after the film takes place. Interestingly, the correct full-color patch is more readily available today.
After Richard makes his speech for the Doctor/Professor at the college who tells him to go live a life, as he is storming out he passes a kid wearing a Dead Kennedys T-shirt. It is supposed to be the 1960s. The Dead Kennedys formed in 1978.
The novel 'Rising Sun', by Michael Crichton, not published until 1992, is in the bookcase next to Richard as he speaks to Art who has just proofread the manuscript of Windmills. Pimentel wrote the Windmills manuscript in 1980.