(500) Days of Summer is such a film as it features a non-chronological format as it went back and forth between a 500 day relationship between a boy and girl.
The early days are bright and happy (complete with dance numbers) and the latter days are dark and depressing.
The film also reminded me of Eternal Sunshine of the Spotless Mind, minus the whole memory erasing scenario.
Joseph Gordon-Levitt and Zooey Deschanel are too young actors on their way up and thought that they had really good chemistry together in this film.
This film was definitely a gem that I highly recommend.