Joel Duscher’s review published on Letterboxd:
This isn’t a fun new theory but the fact that we, the audience, see Phil Connors’ dead body when he throws himself off a cliff and has been dead in the world of the movie for multiple hours before we see his corpse means that his repeated day isn’t a reset for the whole world. It instead means every restart causes another parallel timeline where Phil loops back but the rest of the world keeps moving forward.
This is a very important distinction.
It means there are hundreds of timelines out there where Phil Connors is dead and the world is a much better place because he is a BIG UNLIKABLE CUNT.
Anyways the movie is a classic for a reason four stars or whatever.