ADDED: If you watch this featurette about the movie, with some of the same material from the trailer, the difference should pop out.
AND: "A Serious Man" also has a big anachronism problem:
Although the film is plainly set in the summertime, the only reference to the year in which the film is set is a scene in which a calendar can be seen -- it shows the months of June and July 1967. One of the sub-plots in the film involves a representative from the Columbia Record Club calling Gopnik at his office regarding non-payment for record albums that were sent to him. The record club representative attempts to explain to Gopnik how the club works and goes on to mention that the club's current monthly selections are Santana's Abraxas and Cosmo's Factory by Creedence Clearwater Revival. These albums were released, respectively, in September and July 1970.Link to Wikipedia, which you shouldn't read if you haven't seen the movie. It's full of spoilers.