From what I understood from X-Men: Days of Future Past, it happens in the future, many years after The Wolverine (2013). Why then do Xavier and Magneto meet Logan in 2013? They must have been sent back in time by Kitty to warn Logan, but why warn him in 2013, and then take his help only many years later (ie., in DOFP)?
It is possible that they merely knew the Sentinels were becoming more and more advanced.
We see the Mark I Sentinels in 1973 with the Mark X (ha!) being the super-powered ones we see in 2023-D (D meaning the Dystopian future).
Considering this scene with them recruiting Wolverine takes place in 2015-D we can assume the Sentinel program is probably advanced to a point and revealed at a point around this time that Charles & Erik realize they need to put aside their differences, team up, and get every mutant they know about to join their cause and prepare for a fight together as a mutant force.