Today's Trailer: 'Dr. Who: The Day of the Doctor' The Day of the Doctor - a 75-minute special marking the 50th anniversary special of the venerable British sci-fi series - is so big that it will be simulcast into theaters around the globe. In fact, it's so big that it features not one, but two Doctors - the outgoing Matt Smith and his predecessor David Tennant - and one John Hurt, who already appeared as a special guest Doctor in an episode that aired last season. This short trailer is packed with all kinds of fantastical special effects, albeit with a seriously dark tone that show scribe Stephen Moffat has said will propel the show forward and redefine the Doctor as Peter Capaldi takes over the lead role following this year's Christmas special.