Not sure if this has already been discussed or not, but I think the bartender knows what's going on. Maybe he's God or a higher power putting Phil through this. I've seen this movie at least 25 times and I've always thought he had something to do with it.
1. If he is a higher power there to observe, he purposely rarely speaks just observes. He never gives himself up to Phil. By the end of the movie, Phil knows about almost everyone in town but there's no evidence he got to know the bartender.
2. The movie is directed as such as they show the bartender in single shots almost if not every time Phil speaks to him. Why is such a minor character with very few lines get so many scenes of his reactions to Phil? I think this is a subtle clue the writers/director are trying to show us.
3. My opinion is that there's an higher power at work. Phil is a self centered jerk (to our pleasure most of the movie) but as he lives the same day over and over he eventually comes to care for the town and their people. Once he's became a better person, February 3rd finally comes. So with that said, it's not out of the realm of possibly that God is there watching.