Many things confirm that the X-Men films are not in the 90s. X-Men: Origins Wolverine made that happen but they are just continuing on with Days of Future Past. It may be fixed, it may not but the timeline is more accurate if its based more on Singers version as XMOW was ignored on some parts to make the film they wanted. It's a continuity error but hopefully explained in Days of Future Past or another movie hopefully.
I know but more from Singers part makes it take place later. It's a continuity issue but with continuity, Singers version is at its best. With Days of Future Past, the the commercial for Trask Industries, it makes it later as do many other things.