My two cents about when this movie takes place: In the first film, they don't even mention a year -- I think they just say, "Present Day," and the movie came out in the early 21st century. I think viewers should be elastic in when it actually takes place. It would've been easier if they had used the phrase, "sometime in the near future," so then they could've said for this movie in the very beginning, "sometime in the past."
The only time we know for sure the actual time period in the X-Men films is when we see Magneto as a child in World War II. Also, in the Wolverine film, we know he was a child more than 150 years ago in the 184os, and we see Logan and Victor Creed in various times, from the Civil War up to Vietnam. So we know both Wolverine especially and Magneto have long lives.
I don't think it's so vitally important we know an actual time period. If you want to give it a pseudo-period piece feel, have the men wear hats and the women long skirts, for crying out loud.