According to Ramis' DVD commentary, Danny Rubin's original script and the film as it was actually released are different in several ways. The original script began mid narrative, without explaining how or why Phil was repeating Groundhog Day. The filmmakers believed the audience would feel cheated without seeing Phil's growing realization of the nature of the time loop.
Rubin had also originally envisioned Andie MacDowell's character Rita reliving the day with Phil, and portrayed the pair as being stuck together in the time loop for far longer than the film showed, possibly for thousands of years (Phil tracked time by reading a page of a book each day and had managed to read through the entire public library).
Reports regarding how long Phil is trapped in the time loop vary widely. Ramis states in the DVD commentary that he believes 10 years pass. However, in an e-mail response sent to Heeb magazine, Ramis said, "I think the 10-year estimate is too short. It takes at least 10 years to get good at anything, and allotting for the down time and misguided years he spent, it had to be more like 30 or 40 years."
According to Stephen Tobolowsky, Ramis told him that the entire progress of Groundhog Day covered 10,000 years. "I always thought that there were nine days represented [in the film], and Danny Rubin, the writer, said that he felt something like 23 days were represented in the movie, [but they lasted] over 10,000 years."