In the movie "Groundhog Day", how long did Phil end up staying in Punxsutawney*?

[Revtim]

@William V.

There is also a group of fans who believe that Ned Ryerson (the annoying insurance salesman) was *also * stuck in Groundhog Day, repeating the day over and over again. Not sure I believe it, but it’s an interesting theory.

Why do they think that?