September 27 is the 270th day of the year.
- 1944, Wednesday: Marty McFly and Verne Brown arrived on this day to find Doc's Fance-O-Dance dancing shoes. Later that day, Marty ended up in the army, leaving Verne to help get him out, but unable to until the next day.
- 2006, Wednesday: Thomas F. Wilson uploads The Question Song to YouTube.
- 2013, Friday: Back in Time: The Unauthorized Back to the Future Chronology is published.
- 2015, Sunday: The video game LEGO Dimensions, which includes Christopher Lloyd and Michael J. Fox reprising their roles as Dr. Emmett Brown and Marty McFly, is released in the United States.