During Jack's flashback scenes, he is in pre-World War II and using the name Jack Harkness; however, he didn't use this alias until World War II according to the earlier episode Captain Jack Harkness (2007).
Though this may have been a goof, Captain Jack Harkness jumped through time going billions of years into the future where he was given the ability to not die for a very long time (The Parting of the Ways (2005)) before going back to earlier times. Though this isn't completely explained, as the Doctor said, time is "a big ball of wibbly-wobbly, timey-wimey... stuff."
Though this may have been a goof, Captain Jack Harkness jumped through time going billions of years into the future where he was given the ability to not die for a very long time (The Parting of the Ways (2005)) before going back to earlier times. Though this isn't completely explained, as the Doctor said, time is "a big ball of wibbly-wobbly, timey-wimey... stuff."
Jack Harkness mentions eating dinosaur meat after the asteroid hit. Torchwood shares continuity with Doctor Who (2005), in which the extinction of the dinosaurs was caused by the crash of a deep space cargo freighter from 65 million years in the future in Earthshock: Part Four (1982).