"Day One" is the second episode of the first series of the British science fiction television series Torchwood. Directed by Brian Kelly, the episode was first broadcast on the digital channel BBC Three on 22 October 2006 with the series pilot, "Everything Changes", and later repeated on terrestrial channel BBC Two on 25 October. It was the first work in the Doctor Who universe to be written by future Doctor Who showrunner Chris Chibnall.