Everyone thinks it's another one of those "manic pixie girl" rom com movies that were all the rage in the mid 00s but it's not. It's more of a story about Tom's inability to have a healthy relationship with just about anyone. He builds this ideal girl in his head for Summer, falls for her, but she's just not into him. For her Tom is just a fling, that's it. People wanted the two to be together but she just never had feelings for him. And he doesn't learn his lesson at all because at the end he does the same thing again with another woman named Autumn thus further proving it's all going to happen again. they meet because they have a similar interest in ONE topic and she even initially declines his offer for coffee. He builds these women in his head without actually taking them for who they are. He constantly falls for the wrong women. like the changing of the seasons.

[–] jacksilver@lemmy.world 8 points 1 week ago

I always felt it was a little bit more open ended, possibly even hopeful at the end.

Him finally moving past the 500 days of "summer" to find autumn would imply that he's "changed with the seasons" and has learned more about himself during his relationship with summer. There are definitely allusions to him potentially sliding back, but it's not something the movie really commits to in its ending.