The film deliberately does not show the year of each scene- nor when time jumps occur, as the audience is left to witness the transitions of time themselves, based on changes in the appearances of the characters, as well as cultural and technological changes that have occurred. Central character Mason shows very little noticeable change in the early years of filming, whilst looking noticeably different during late childhood and adolescence.
EDIT If you are a fan of Patricia Arquette and her TV Show Medium, you can guess the years base on her haircuts, because they are basically the same she wore in the sitcom.
