Star Trek: Deep Space Nine - Season 5 Episode 22 Children of Time

Stardate: 50814.2. The DS9 crew discovers a small colony on a remote world that was originally populated by them 200 years earlier due to a time travel accident with the Defiant. The current colonists' lives depend on making sure that the accident happens again, even though they've now forewarned the crew that it will happen. Each crew member needs to decide if they are willing to give up their lives on DS9 in order to preserve the history of the colony.