As others have pointed out, this film is essentially "Groundhog Day" set at Christmas with a younger protagonist. That's not a revelation. Anyone who has seen both films will catch the clear references to "Groundhog Day" in this film. And if I were rating this film based only on originality, it would get a very low score indeed. But the target audience for this probably will not have seen "Groundhog Day," and even so, the idea of repeating time is was not necessarily invented for "Groundhog Day." (See, for example, "12:01," which was a television movie released in the same year as "Groundhog Day.")
The premise is simple. Pete's Christmas does not go well. His parents forget to get him a gift, his brother blames him for things he didn't do, and his grandfather visits only to feel slighted and leave. Oh, well. Not every Christmas can be good. When Pete awakens the next day, it's Christmas yet again. And again. And again, and so forth. And as we go through probably hundreds of Christmases, Pete learns and one by one tries to right the wrongs of the first Christmas. In doing so, he learns a fair amount. I'll give an example that won't ruin much of the film, but it's a bit of a spoiler, so skip the next paragraph if you'd rather not have any more of the plot revealed.
As part of Christmas day, Pete and his brother play in a football game against the neighbors. At first, the neighbors win, as, it seems, they always do. But given the chance to relive the same day repeatedly, Pete realizes that he can win the game since he knows what the other team will do. And so he does--only to find out that his brother, the football star, is not satisfied. So Pete finds another way to win the game, this time addressing his brother's concerns. (Oh, and the solution seems silly and contrived.)
Certainly not the greatest film ever made, "Pete's Christmas" does have a certain charm and does seem to have its heart in the right place. And Bruce Dern as the cranky grandfather is lots of fun.