According to Den of Geek the release of X-Men Origins: Wolverine has been moved forward a few days.
The original plan was for the film to get its release on Friday 1st May, but thanks to a quick shuffle of the schedules, it’s now moved into April.
The new date that you need to mark in your diaries is Wednesday 29th April 2009.
This isn’t a big shift and a small change in date is quite common (just like reshoots). The following weekend Star Trek is released so Fox will be trying to get more $$$ before the other summer players show themselves. Considering the future direction of the X-Men franchise depends on the success or failure of Wolverine, this is a good move.
Update: This may only be the case in the UK.