In the 2014 film X-Men: Days of Future Past, Wolverine spends roughly 4-5 days in the body of his younger self in 1973. He is sent/held there by Kitty Pryde, who must maintain her concentration while projecting Wolverine's consciousness back in time.
How long must Kitty remain by Logan's side, projecting his consciousness to the past? Is Kitty really sitting there using her powers for multiple days, or is there a time dilation effect present?
Note: For purposes of the question, we'll restrict the discussion to the theatrical version:
where Rogue does not take Kitty's place.