Two very different films: One Day and Source Code.
About as different as possible in style, intent, audience... yet these two films share their most basic premise, the longing to rework the past, to have done things differently.
Source Code is a sci-fi jump-back-in-time-to-avert-the-disaster flick. I'm not sure the logic actually stands up to much scrutiny. Though the film has pretensions to a "think" piece, it's really just there to blow up the train (a lot). The film's title is irritatingly pointless. But the hero is likable and heroic, the girl appealing, the egotistical and ruthless military(ish) superior properly e & r, and the sympathetic-ally dependable... what more do you expect of a summery action movie?
One Day, on the other hand is an art house flick. Nicely photographed, well cast and acted, thoughtful. Good. But I think it was actually hurt a bit - at the box office certainly - by its art-house aspirations. These led the filmmakers to, I think, over-emphasize the unlikable aspects of the hero until, well, you didn't much like him. Also to take the female lead's character one step too far, to too dark and serious an ending... at least for popular taste. But the film's ending is lovely and almoooost redeems those choices; though I liked the film quite a lot and find it recurring to me - I wanted to love it.
Maybe it's appropriate to these films' deepest theme - a wish to change what's done - I wish I could go back and tweak both films for the better. (My better any way!)