Harold Ramis cut the reason Bill Murray's day keeps repeating in 'Groundhog Day'. His ex-girlfriend cast a curse on him with his broken watch (set at 5:59). His curse of 10,000 days was broken when Rita kisses him and can actually hear tinkling music, signifying the curse being lifted.

Good decision getting rid of that. The film is timeless because you are not necesarilly given a reason as to why this is happening. The witchcraft would have deteriorated away from the film's, ahem, spell. The full Groundhog Day reveal can be found HERE