Danny Rubin was the dude who wrote the screenplay for Groundhog Day and brought it to Harold Ramis to direct. But the two quickly differed in their opinions on how cheery or dark the final movie should be. Danny Rubin originally wrote the script as if Phil Connors were stuck in Groundhog Day for 10,000—count 'em— 10,000 years.
Harold Ramis, on the other hand, pegged it somewhere around 10. That's a pretty huge difference. But you can see the Danny Rubin darker side come out in the montage where Phil Connors kills himself in a half-dozen brutal ways only to wake up again in his B&B bed.
In the end, it's probably best that Harold Ramis won out and that Phil's time in Groundhog Day was a long (but manageable) 10 years. At least in this interpretation the movie has a positive spin—we're willing to bet that in Danny Rubin's version Phil would have wound up staring off into space and drooling after being stuck for 10,000 years.
Oh yeah: Rubin's original script called for the Rita character to start her own time loop after Phil's had ended. But that wouldn't make any sense according to the logic of the film, since Rita is already a good person and would have nothing new to learn.