BAM is celebrating Valentine’s Day with 4 days of films about romance at its Long Weekend of Love series screening Friday through Monday. There are lots of great titles on the slate, but I’d go for Sunday’s triple-header of Richard Linklater’s “Before” trilogy, starring Ethan Hawke and Julie Delpy. The critically-acclaimed and beloved trio of movies, Before Sunrise, Before Sunset, and Before Midnight, follows a love story that begins when two strangers spend one fateful night together in Vienna. The films were shot and released at nine-year intervals, giving the effect of providing the audience with snapshots of the protagonists’ lives. The films will be screened chronologically starting with Before Sunrise at 2pm, and although you can choose to watch them individually, you can get 25% off the ticket price if you buy a package for all three.