This comedy-romantic story starts with a good concept. It couldn't go anything wrong if you want to kill time with it. The best friend is fun, his scenes are hilarious. But the main characters - the nerd physics and the blond bartender - they seem to have zero chemistry.
The first half is okay, if we just let go "the college student invented a time machine" setting.
The other-half is going nowhere, when the guy get hookup with the machine and keep going back to fix problems. I was expecting something bigger and deeper like The Butterfly Effect movies, or alternatively ending with a bigger picture. Not ends with silly car chasing, the scene is awkward, and no one laughed.
On the other hand, the ending is meaningful in some way. It reveals the differences between man and woman. In a relationship, man can always sensibly stop the loss straightforward when he feels tired, even he's hurting inside; By contrast, woman mostly hooked up with her partner after a long period of devotions and commitments in a relationship, it's hard for them to cut off the memories and emotions.