All our yesterdays: 15 times Star Trek altered the timeline

2009’s Star Trek isn’t the first entry in the franchise to use timeline manipulation as a major plot point. Of the 10 films leading up to the J.J. Abrams-helmed reboot, almost a third featured time travel in their narrative mechanics. In 1986’s Star Trek IV: The Voyage Home, Kirk and crew traveled back to our time to steal an endangered humpback whale out of captivity for, uh, space reasons; the plot was really just an environmentally friendly MacGuffin designed to facilitate a lot of genial fish-out-of-water jokes. Star Trek: Generations (1994) used a semi-magical cosmic nebula to pit Kirk and Jean-Luc Picard against a villainous (if overmatched) Malcolm McDowell. And Star Trek: First Contact (1996) found Picard’s eternal enemies the Borg jumping back to a pivotal moment in Earth’s past: the discovery of warp speed and the titular “first contact” with an alien race. Disregarding usual protocol about not meddling with the past, the Next Generation team pitches in to make absolutely sure history happens the way it’s supposed to. [Zack Handlen]

The series’ first major foray into time travel—if you put aside the relatively minor three-day rewind in “The Naked Time”—sends a wounded Enterprise back to 1968, where the timeline is corrupted by Kirk’s impulsive decision to beam aboard an Air Force pilot who was chasing the wounded starship. At first, Spock decides that the future might not be affected by the mishap, as he somewhat rudely observes that their captive pilot made no “relevant contribution” to history. But when the Vulcan first officer takes a second look at his history database, he realizes that the pilot’s son became a space exploration hero, so the Enterprise crew can’t just fire the pilot out of the airlock without sweating the consequences. The mess grows from there, but ultimately, Kirk authorizes a plan to slingshot the Enterprise around the sun, a maneuver that conveniently sends the ship slightly backward in time before it goes forward again. That way, the crew can tidily put everything on 1968 Earth back the way it was before returning to their proper time—the first of many times Star Trek would hit the time-travel reset button. (The slingshot trick in particular would be reprised in the similar “back to the 20th century” plot of Star Trek IV: The Voyage Home.) [John Teti]

Long before they could be baffled by the “barbaric” customs of San Francisco in the ’80s, Kirk and Spock traveled to Depression-era New York in pursuit of a whacked-out McCoy. The journey’s nowhere near as perilous—it’s a simple matter of walking through a doorway—but the stakes are just as high. Kirk and Spock are only permitted through to bring back the good doctor and restore their timeline, as his passage through the doorway has removed the Federation from existence. Kirk falls for a do-gooder played by Joan Collins, whose life is saved by a rambling McCoy. Unfortunately for the lovers, her survival is what’s threatening Kirk’s future. The captain makes the ultimate sacrifice (on her behalf) by leaving her to die in the street—which is no way to treat Alexis Colby, but at least their timeline’s restored. [Danette Chavez]

If you also felt that Tasha Yar was short-shrifted in the TV-deaths department, then this crowdsourced storyline should help you make peace with her departure. The Enterprise D comes across a time rift that spits out its predecessor, the Enterprise C, which was destroyed 22 years ago in battle while responding to a distress call at a Klingon outpost. Only Guinan notices that the ship’s emergence has mucked up the timeline, which has left the Federation at the losing end of a war with the Klingons. She’s also the only one who realizes that Tasha shouldn’t be a part of the crew, because she died in “Skin Of Evil.” But the dismal alternate present is what forces Picard to consider the unthinkable—sending the outgunned Enterprise C back through the rift, effectively sentencing the crew to death. Tasha decides she’d rather have her death count for something, and transfers to the Enterprise C’s crew to give them a fighting chance. [Danette Chavez]

Typically when Next Generation wanted to put its characters in an amusing old-timey context, the show would just have the crew toddle on down to the holodeck, where nothing could possibly go wrong! But the “Time’s Arrow” two-parter sends the crew back to 1890s San Francisco for real, as they track down a race of time-bending aliens who are harvesting “neural energy” from citizens of the past. In practice, the alien storyline takes a backseat to the antics of Data and an unceasingly meddlesome Mark Twain. Although Jerry Hardin’s crotchety performance as Twain can be trying, the author provides the soul of the story’s finale, as Twain ends up in the future but volunteers to return and set history straight again. This makes him the rare Star Trek transplant from the past who manages not to turn into a total idiot when he arrives in the distant future. Maybe there’s hope for us pre-wrap rubes after all. [John Teti]

The episode that launched a quarter of a million Enterprises also saw the brief return (and promotion) of Wesley Crusher. Worf becomes an uneasy rider on a trip through all the alternate universes that Data theorizes are out there. He retains some memories from the Prime timeline (see, that’s already coming in handy), so he knows that there’s something… off about “Captain Riker” and “Lieutenant Crusher.” He has trouble adjusting to his new universe, and one of his blunders costs Geordi his life. Eventually, Worf learns that his post-bat’leth victory lap took him through a space-time fissure, which put him in a state of quantum flux. A sudden battle with the Bajorans further damages the fissure, which then produces over 200,000 Enterprises—all in the same universe. Going back through the fissure sets things right, which means that, yes, Wesley leaves the Enterprise again. [Danette Chavez]

In the Next Generation finale, omnipotent tormentor Q challenges Jean-Luc Picard by bouncing him between not just two but three separate eras of his life—the present day of the show, the early days of Picard’s Enterprise career, and his post-Starfleet future. As Picard finds his bearing amid the time jumps, Q eventually reveals that the captain must find a way to contain an “anti-time” anomaly that, if left unchecked, would reverse the formation of life on Earth in the distant past and retroactively destroy humanity. The logic of the anti-time anomaly is somewhat self-contradictory, even by the standards of sci-fi paradoxes. But Picard’s humanity-saving epiphany—that he essentially created the anomaly himself by looking for it—is a brilliant flourish of writing that sends the series off on an aspirational note, with Q saluting humans’ capacity to consider possibilities they had never imagined before. [John Teti]

As time travel became a standard element of the Trek verse, concerns over protecting the current timeline from disruption became more critical. Case in point: when Commander Ben Sisko, Dr. Bashir, and alien slug-lady Dax are inadvertently transported to early 21st-century America, they quickly find themselves in the middle of a historic tragedy. The “Bell Riots” of 2024 helped to inspire the transition from the crummy present we know and love to the beatific, civic-minded Federation of the show’s present. When Sisko’s presence inadvertently gets Gabriel Bell—a major symbol of those riots—killed, the commander has to take his place to make sure history unfolds the way it’s supposed to. The result is a (sadly still relevant) two-parter about the ways civil unrest reveals deep-rooted problems in society, and a reminder of all Sisko is willing to risk to stand against those problems. [Zack Handlen]

There’s nothing that says threatening the fabric of space-time has to be serious. When a malfunctioning ship forces Quark, his brother Rom, and his nephew Nog to make an emergency landing on Earth, they find their last-minute maneuvering has sent them to a time when everyone smoked cigarettes and no one had landed on the moon. Ferengi-centric episodes on DS9 were typically comedic, and “Little Green Men” is no exception—as one of the strongest episodes to focus on Quark and his crazy adventures, the hour serves as a mild (and loving) satire of early science-fiction tropes, from the square-jawed military to the pipe-smoking professor and his supportive girlfriend. There’s even time for character development, as Quark once again demonstrates his arrogance by trying to pull a fast one on his army captors. It all makes for a romp without much in the way of stakes, but with some great character moments and a lot of good fun poked at classic sci-fi movie clichés. [Zack Handlen]

Plenty of Trek episodes dealt with time travel before DS9, but “Trials And Tribble-Ations” is the first to show characters traveling back to the events of a previous series; in a way, it serves as a prototype for the direction the new movie franchise would take, dipping in to the nostalgia of the original series while still maintaining its own voice. The plot here is largely an excuse to let the crew of DS9 interact with some of their “heroes,” as the episode uses footage from the classic original-series entry “The Trouble With Tribbles” intermixed with matching footage from the present. The effect is hugely entertaining, allowing the show to both mock and pay homage to the flaws and wonders of its predecessor. As a bonus, “Trials” also introduces the Department Of Temporal Investigations, a group dedicated to maintaining the internal logic of history. They mostly serve as a framing story, but the existence of the department is a helpful reminder that time travel and the shenanigans that result from it are an integral part of the franchise. [Zack Handlen]

Any episode of Star Trek that opens with the titular ship completely destroyed is almost certainly going to involve some fun timeline shenanigans and “Timeless” does not disappoint. Harry Kim and Chakotay arrive on the frozen planet where Voyager crash-landed 15 years earlier due to a miscalculation on Harry’s part (he and Chakotay were flying ahead in a shuttlepod). As they wander through a frozen bridge full of the corpses of their friends, they reveal their plan to use Seven Of Nine’s Borg implant to send a message back in time and stop the accident from ever happening. Voyager was infamous for underutilizing Harry Kim, but seeing the optimistic young ensign transformed into a bitter Captain Ahab figure is surprisingly effective, as is the message the older (and now nonexistent) Harry manages to send to his younger self just before they alter the timeline: “Fifteen years ago, I made a mistake, and 150 people died. I’ve spent every day since then regretting that mistake. But if you’re watching this right now, that means all of that’s changed. You owe me one.” [Caroline Siede]

Thanks to the “lost in space” premise that fueled the show for seven seasons, there was a lot of pressure on Voyager to wrap things up in the season finale. “Endgame” opens decades in the future with the Voyager crew celebrating the 10th anniversary of their return to Earth. It turns out Voyager spent a total of 23 years in the Delta Quadrant, a trip that saw many of the crew members killed or psychologically damaged. In the intervening years, Captain Kathryn Janeway—now an admiral—has been eaten away by the guilt of failing her crew and decides to travel back in time and point Voyager toward a transwarp corridor that could get them home instantly. The setup is mostly an excuse for an older, bitter Janeway to face off against her optimistic younger self in a battle of iron wills. And once the two Janeways finally start working together, they’re able to send Voyager home 16 years ahead of schedule—presumably to far sunnier futures for the entire crew. [Caroline Siede]

Enterprise managed to immediately derail all of the goodwill it had earned in its drastically improved third season by inserting an absurd twist in the finale: After saving Earth, Enterprise is somehow transported back in time to the 1940s and an injured Captain Archer wakes up in an army hospital to discover… alien Nazis! To its credit, the fourth-season premiere leans into that insane cliffhanger pretty well, imagining a future in which alien support allowed Germany to invade the U.S. and occupy the East Coast. “Storm Front” has a lot of fun imagining a war-torn version of Brooklyn in which former New York gangsters lead a local resistance movement. And in giving Archer and his crew the chance to defeat the alien Nazis and restore the timeline, the episode mercifully ended the show’s interminable Temporal Cold War once and for all. [Caroline Siede]