In this movie the premise is that he lives in 2004 and she lives in 2006.

During the scene where Sandra is showing her mom the letters in the restaraunt and telling her mom to look at the date on the letter, she then says it is 2006.

If you look at the poster on the wall behind Sandra Bullock in this scene, it is advertising Tickets to the NutCracker in December of 2004.