Realistic Movies

I watched a movie recently that was pretty well made. My only issue is the director's comments at the end where he states that he spent months researching every aspect to make sure the film was as realistic as physically possible. The movie is set in 1962 and yet right away I noticed they played a song at a dance that didn't come out until 1965. There were many other issues (political and cultural) that I noticed as well.

These may sound like small things, but I think they are pretty important. A song or cultural reference made in a time-period movie that wasn't made til after the fact just shows a lack of understanding on the part of the director. In some movies it doesn't really matter, but in others (especially those that are based on true events) they are very important. How can a character fall in love while a song plays in the background and eventually becomes "their song" when in reality that song wasn't made til 3 years later?

I guess I would just like directors and others to take a second and check the dates to make the movie even more realistic.