The longest take is about 11 minutes long.

The man and woman that Celine speaks to in the courtyard of her apartment are played by Julie Delpy's real parents, Albert Delpy and Marie Pillet.

Though this movie was nominated for Best Adapted Screenplay, the screenplay is not based upon any existing text. However, the Academy rule book says that all sequels are adaptations.

Jesse ('Ethan Hawke (I)') has married a woman because she became pregnant, and they are now in a wedding crisis.
This parallels the story he told in Before Sunrise (1995), about his parents marrying because of his mother's unexpected pregnancy, and their subsequent divorce.

Since the film takes place during the mid-late afternoon, it was the only time of day director Richard Linklater would shoot the scenes in the film.
He felt it added to the hyper reality of the film, and often relied on the actors to get perfect takes at the right time.