I missed the very beginning, did it say what year this starts out in? Doesn't seem very consistent with 20 years ago, Pretty Woman came out in 1990 and I don't remember Starbucks being huge in 1987.
shareThe movie is made in 2007.
The beginning of the story takes place in 1990, which is listed with the high school class info at the beginning of the movie.
Sarah is in the Class of 1990, hence she is 17.
Sarah's brother is an astronomy hobbyist and has a telescope; he tells her that the imminent eclipse is the last total eclipse for 17 years.
When Sarah and the quarterback land in the future, they are told it is 2007, so there's going to be another eclipse in that year. Very handy.
It's mentioned in dialog that Sarah is 34 as her future self.
1990 + 17 = 2007
17 + 17 = 34