Question: Why did the Event Horizon choose to come back after seven years? In fact, why come back at all?
Answer: With the recent Event Horizon prequel comic, it is established that Event Horizon is not in the Warhammer universe and there is a king of hell in the film. His name is Paimon.






Chosen answer: The movie never explicitly says; but science is as yet unsure what happens to a given piece of matter once it crosses a black hole's event horizon, so who knows? The ship could have been thrown seven years forward in time, or far enough away that it took seven years for it to drift close to Neptune. Pick any explanation you like.
The theory that the film is a stealth prequel to the 'Warhammer 40,000' universe has been confirmed by one of the writers, who was a big fan of 40K and said that the setting influenced his writing "either consciously or subconsciously" – because Games Workshop is litigious. But since the Horizon entered into the Warp, time there flows extremely differently from time in real space; while it was seven years for people in real space, it could have been seconds, or thousands of years, for the ship.