Today is the big day for Doctor Who fans. The BBC will be simulcasting around the world the 50th anniversary episode of Doctor Who, which is called The Day of the Doctor. We've collected together all the sneak previews that have been released for The Day of the Doctor below. In The Day of the Doctor episode, of Doctor Who, The Doctors embark on their greatest adventure through space and time. In 2013, something terrible is awakening in London's National Gallery; in 1562, a murderous plot is afoot in Elizabethan England; and somewhere in space an ancient battle reaches its devastating conclusion. All of reality is at stake as the Doctor's own dangerous past comes back to haunt him. The Day of the Doctor stars Matt Smith, David Tennant and Jenna Coleman with Billie Piper and John Hurt. On Saturday, November 23, 2013, The Day of the Doctor airs in the UK on at 19: 50 on BCC One. The Day of the Doctor airs in the United States on at 2:50 PM ET on BBC America.