Tomorrow Is Yesterday

Did You Know?

• The episode was originally conceived as part two to an earlier episode, "The Naked Time"; when the ending to that episode was revised, "Tomorrow Is Yesterday" was reworked as a stand-alone story.
• Associate producer Robert H. Justman devised the original idea for the story, and it was handed to Dorothy Fontana to create a teleplay. Justman received neither credit nor payment for doing so.
• Roddenberry's agent charged the studio up to $3,000 for his own stories and rewrites.

Plot

The USS Enterprise is flung back to 1960s Earth after passing too close to a high-gravity "black star." It appears in the upper atmosphere and triggers military radar. The Air Force scrambles an F-104 fighter piloted by Captain John Christopher to investigate the UFO. Kirk, worried the jet might carry nuclear weapons, uses the tractor beam on it, which tears the plane apart.

To save Christopher, the crew beams him aboard. Kirk initially decides the pilot cannot return to Earth, fearing he would alter history. But Spock discovers that Christopher's future son is essential to a Saturn mission, so Kirk changes his mind. Learning that Christopher's wing cameras filmed the Enterprise, Kirk and Sulu beam down to the airbase to confiscate the film and other evidence.

An Air Policeman catches them, accidentally triggers an emergency signal on Kirk's communicator, and is beamed up. Kirk and Sulu continue; Kirk gets caught again, and Sulu escapes. Spock, Sulu, and Christopher—who knows the base—beam down to rescue Kirk. After subduing Kirk's guards, Christopher grabs a gun and insists on staying behind.

Spock, expecting this, sneaks up and knocks him out with a Vulcan nerve pinch. Back on the ship, Spock and Scott propose a risky escape: slingshotting around the Sun to break free and return to their own time. A small error could destroy the ship or send them to the wrong era. Kirk approves.

As the Enterprise begins the maneuver, time on board reverses. Christopher is beamed back into his fighter at the exact moment of first contact, erasing his memory and preventing any film from surviving. The Air Policeman is returned similarly. The Enterprise then successfully reaches the 23rd century.

Reference in further Star Trek stories

The slingshot maneuver introduced in this episode was later used to send the Enterprise back to 1968 in "Assignment: Earth," and it is assumed the same method brought the ship home after that story. In the second issue of IDW's Assignment: Earth comic series, Gary Seven and Roberta Lincoln secretly intervene in the events of "Tomorrow Is Yesterday" to prevent the Enterprise from altering history. Because of time travel quirks, the Enterprise crew has not yet met them, though this is Seven and Lincoln's second encounter with the ship.

The crew used the slingshot maneuver again in Star Trek IV: The Voyage Home to reach 1986, and later to return the captured Klingon Bird of Prey, renamed Bounty, to 2286. In "Penance," the twelfth episode of Star Trek: Picard, Picard notes that Kirk's Enterprise employed the method multiple times and suggests doing the same to restore their timeline. When it is pointed out that Kirk succeeded only because Spock handled the calculations, Jurati negotiates for the captive Borg Queen's help.

The Borg Queen, Admiral Picard, and his crew then fly La Sirena back to 2024 in the following episode, "Assimilation." The Star Trek Star Fleet Technical Manual includes a description of how its contents were accidentally downloaded into the main computer of a U.S. Air Force facility in Omaha—specifically Offutt Air Force Base, headquarters of the Strategic Air Command, referred to as the Omaha Installation in the script—during the accidental time trip the Enterprise took in this episode.

Reception

A 2009 Tor.com review gave "Tomorrow Is Yesterday" a 5 out of 6, highlighting its portrayal of "hope and optimism and excitement about the new frontier" before the first moon landing. Notably, the Apollo 1 disaster occurred the day after the episode first aired. Zack Handlen of The A.V. Club rated it a 'B−', calling it "so-so" and "passable." In 2016, SyFy placed it 11th among Star Trek time travel plots. CBR included it in a 2018 list of the top twenty time travel episodes across all Star Trek series. That same year, BuzzFeed recommended it as a better introduction to the franchise than the pilot, praising it as "beautiful, witty, and really makes you think." In 2019, Nerdist ranked it the sixth best time travel episode in all of Star Trek.