The characters entered Harvard in 1967 and presumably were to graduate in 1971, and it shows them as apparently the first class involved with the draft lottery, which affected only seniors. However, the first class involved with the lottery was actually that of 1970, and the movie accurately shows the first ball being pulled from the drum with a date of September 14 in the drawing held for the 1970 class.
The clothing worn is obviously brand new and never has the scruffy look of the era.
Students are seen dancing to the Rolling Stones record "Street Fighting Man" moments after President Lyndon Johnson's television address in which he announced he was not running for reelection. However, that speech was delivered on the last day of March 1968, while the song had not even been recorded yet and was not released until the last day of August 1968.