I like the idea of an honest non-fairy-tale could-happen-to-you relationship story. Because that's life, and just because a relationship ended doesn't mean that it wasn't based on love. It just wasn't meant to be.
I think everyone has a "Summer" in their lives. Someone you have to get over with before you finally meet the right one; your "Autumn". Just like, you know, a "Robin" before you meet "The Mother" ;)
AJ Rafael - Five Hundred Days
On another note, I stumbled upon this video and as a die hard 500 days fan, I absolutely love it. I hope you do too. ;)