Bryan Singer just confirmed on his twitter account that Days of Future Past will receive the coveted Memorial Day tent-pole position in 2014 meaning it will come out Friday, May 23rd, 2014.
Memorial Day Weekend in the USA is one of the biggest selling weekends for movies and so companies like to put out films that will give them a strong opening. For example, this year saw the release of Hangover III which had a 42mil opening weekend (and it is a Rated R film) and Fast Six which did 97mil . This means that Fox has a lot of faith in this film which hasn’t even finished production yet.
Though, with the literal all-star cast which includes several Oscar winners and some really hot names right now, they probably call this movie a win-win regardless.