Tomorrow is Yesterday (episode)
The Enterprise is hurled back in time to the year 1969, where the US Air Force sights it as a UFO. The crew must find a way to erase evidence of their visit before trying to get back to their future home.

Summary

Teaser

At an Air Force base in 1969, a technician by the name of  detects something on his RADAR. At first, his commanding officer believes it to be an enemy aircraft. The signal is over the base near Omaha, Nebraska, but the strange part is that it just appeared. It is as if it simply dropped out of the sky.

Interested by the strange appearance of this aircraft, Webb's commanding officer orders someone to go up there and take a look. He believes they may have a real UFO on their hands. Outside, an F-104 Starfighter is launched. In the sky, the starship  is gliding through the clouds.

Act One
"Captain's log, Stardate 3113.2, subjective time: We were en route to Starbase 9 for resupply when a black star of high gravitational attraction began to drag us toward it. It required all warp power in reverse to pull us away from the star, but like snapping a rubber band, the breakaway sent us plunging through space, out of control to stop here, wherever we are."

Except for secondary systems, everything is operational and they are heading on impulse power. Chief Engineer Montgomery Scott brings on auxiliary power from engineering, and Captain James T. Kirk asks all departments to report damage and casualties to First Officer Spock. Kirk asks Uhura to contact Starfleet Control, to advise them of the black star's close proximity to Starbase 9. Casualty reports show nothing more than minor injuries. Scott reports that warp engines are offline, and he is holding them at impulse in orbit over Earth. The breakaway from the star threw the ship to Earth. They are, however, in a low orbit, and Kirk orders Sulu to use impulse to rise to a higher orbit. Sulu reports that the helm is answering but is a little sluggish.

Uhura reports that there is no response on any standard Starfleet channels; however, she is getting something on another frequency. A radio broadcast states that the first manned moon shot is to take place on Wednesday. Kirk recalls that the first manned moon shot took place in the late 1960s. Spock concludes that the Enterprise is also in the 1960s, having been thrown backward in time by the black star's whiplash.

Uhura reports that she is picking up ground-to-air transmissions. A military craft is approaching the Enterprise, fast. The craft, designated Bluejay 4, is gaining on the UFO (Enterprise). Kirk orders Sulu to gain altitude faster. Bluejay 4 states that the UFO is climbing, and he will go in closer. As he raises altitude, Blackjack (the Omaha base) states that Bluejay 4 should be close enough for visual contact. Bluejay 4 spots the Enterprise, which is climbing in the sky, amazed at its size. He starts to describe the UFO, and tries to determine what purpose the cylindrical projections might serve. Blackjack states that backup forces should rendezvous in about two minutes, but Bluejay 4 remarks that the UFO is not going to be there by then. Blackjack gives order to shoot down the UFO, or at least disable it. Spock concludes that the aircraft may be armed with nuclear warheads, which in the Enterprises severe condition, could possibly cause serious damage to the hull. Kirk orders Scott to lock on with a tractor beam, but Spock advises against it. Scott locks on, regardless, and the aircraft begins to break up. Kirk orders the pilot beamed aboard. He goes to the transporter room to meet the pilot, and welcomes him aboard. The pilot is surprised to learn that Kirk speaks English, and gives his identification as Captain John Christopher of the United States Air Force, service number 4857932. Kirk remarks that the captain is among friends, and introduces himself. Captain Christopher asks Kirk who they are, and what happened. Kirk states that all will be revealed in good time, but Captain Christopher is understandably impatient.

On the bridge, Spock reports that the aircraft has broken up. They turn off the tractor beam, and Kirk takes Christopher to the bridge. Christopher seems surprised to see a woman in the halls. Christopher admires the size and complexity of the ship, and as Kirk explains that the ship is one of twelve like it in service of the United Earth Space Probe Agency. He freely admits that he is from the future. On the bridge, Christopher (after joking about "little green men") is taken aback by Spock's skin tone. As Kirk allows Christopher to look around the bridge, Spock expresses his concerns about their guest to Kirk privately.

As Christopher looks around, Spock reports that most main systems have been restored, including the main deflector, which will prevent them from being detected again. Spock also expresses concern for Christopher's presence. He states that Christopher cannot return to Earth, as this could alter the course of history. Kirk states that this is an annoying conclusion, but accepts the truth. He asks Spock to get Captain Christopher some more comfortable clothes, and to bring Christopher to his ready room.

In his quarters, Kirk makes a computer recording.

"Captain's log, supplemental. Engineering Officer Scott reports warp engines damaged, but can be made operational and re-energized."

Kirk also gets annoyed by the computer's frequent references to him as "dear". Kirk asks Spock to fix the computer's affection. Spock explains that the computer had recently been overhauled on the female-dominated planet Cygnet XIV (who thought the computer needed a personality). Christopher, who is now wearing a Starfleet uniform in place of his orange pilot's flight suit, finds the computer system amusing, and would love to see how the dilemma works out. It is at this point, that Kirk breaks the news to Christopher that he cannot be sent back with information he now knows from the future. Christopher asks about his disappearance, but Spock says that Captain Christopher made no relevant contribution to history. Christopher says that this is an outrage, having a wife and children back on Earth, something which seems to catch Spock's attention. He says it is his duty to report what he has seen, but Kirk says that the risk is impossible. Kirk offers his heartfelt apology.

Scott calls to tell Kirk that the engines will be operational in about four hours, but they have nowhere to go in this time. Kirk understands. Christopher finds some comfort in the fact that Kirk and his crew cannot go home themselves.

Act Two
"Captain's log, Stardate 3113.7, subjective time: Our engines are being repaired, but we are still locked in time, and we have aboard a passenger whom we do not want, and we cannot return."

Finally getting fed up with the computer, Kirk asks it to record that it either be repaired, or scrapped, which seems to take care of the computer problem. Spock calls Kirk, stating that he has new information regarding Christopher. Kirk orders Spock to report to his quarters, and that he will call Captain Christopher. However, Christopher does not respond to Kirk's hails. Kirk orders a security alert, noting that Captain Christopher is not in his assigned quarters. Kirk hypothesizes that he may be trying to escape, and goes to find him.

Christopher is indeed trying to escape, but runs into security officer Bobby on his way to the transporter room. He takes out the security officer, and acquires his phaser. Entering the transporter room and pointing his phaser at Kyle, Christopher tells Kyle that he wants to be transported to the surface immediately, but before he can complete his escape, Kirk comes, disarms Christopher, and knocks him out. In sickbay, Dr. McCoy reports that the injuries are superficial, and Kirk sympathizes about Christopher's want to escape. It is at this time that Dr. McCoy says that they too are just as stuck as Christopher. They can't beam down the entire crew, as it would be too great a disturbance in the timeline. Kirk however, says that Enterprise is not at that situation yet, but even if they do get back to their time, Christopher would be useless, archaic. McCoy says that he may be able to be retrained, but Christopher says that he cannot forget his family. He remarks that he is feeling fine, and Spock comes to sickbay. They cannot keep Christopher aboard, because his son, Colonel Shaun Geoffrey Christopher, did make an historic contribution, heading the first Earth-Saturn Mission. Christopher remarks that he has no son, to which McCoy responds, "yet". Kirk realizes that they must find a way to return Captain Christopher, and Christopher himself muses of the fact that he someday will have a son.

In orbit of Earth, Spock states that the biggest problem they must deal with is that Christopher's plane wreckage landed in open land ("an open section of Southern Nebraska"), so search parties will know that he wasn't on the plane. Also, Captain Christopher informs them that his radio conversation was recorded, and that his wing cameras were recording the Enterprise. Kirk remarks that these UFO sightings were usually taken for explainable things, but Spock remarks that their tractor beam destroyed the plane, making them nothing else but a genuine UFO. Kirk then asks about returning them to their own time. Spock has a theory, albeit complicated, which may work. Kirk then makes a plan; they need to destroy the hard evidence of their presence, so that if Christopher reports, there is nothing to support his claims, and he simply joins the ranks of one of thousands who has seen a UFO. Christopher then offers his help, and he sketches out a layout of the base on a PADD.

At the base, Kirk and Sulu beam down, Sulu with a bag for the tapes. They are a bit disoriented at first, but soon find the correct room. They force the door open with little difficulty using their technology. Upon entry, Kirk starts to look for what they need, and soon finds the audio tapes. On the Enterprise in the transporter room, Dr. McCoy is getting nervous, but Spock reassures him, noting that stealth missions are much more complicated than others. McCoy starts to get annoyed, and asks Spock whether he should be working on his time warp calculations, to which he calmly responds, "I am."  Back at the base, Kirk and Sulu finish getting the tapes, when a Security Police staff sergeant enters. He orders them to give him the belts and the bag, with the tapes inside. On the ship, Spock now agrees with McCoy and starts to think it has been too long, so he calls the captain. The security officer opens one of the communicators, transmitting an emergency signal. Spock orders an immediate beam-up, only to find that they beamed up the wrong man. They now have two undesired passengers aboard, and the sergeant is frozen out of both surprise and fear. Kirk calls Spock, reporting that they now clearly have another problem.

Act Three

"Captain's log, Stardate 3113.9, subjective time: First Officer Spock recording. Due to an unfortunate accident, we have taken aboard another unwanted passenger."

Kirk informs Enterprise about their "surprise package", and asks them to keep him in the transporter room. After finishing up in the audio tape section, both Kirk and Sulu go to retrieve the photographs of the Enterprise. They find a darkroom containing freshly developed 16mm movie film of the Enterprise, but set off a silent alarm. They finish collecting the film, but after a small brawl with some security officers, Kirk gets caught. Sulu however, seems to have disappeared. He managed to beam up, with the tapes and film, and Kirk calmly explains to the curious guard that it was only he who was prowling about.

On the Enterprise, Scott reports that warp engines are ready for re-firing. Spock orders them to be, so that they can have full power. Down on the surface, Kirk is being interrogated by the guards who caught him. Kirk jokingly references that he got in to the base by popping in out of thin air. Lieutenant Colonel Fellini picks up Kirk's phaser, mistaking it for a radio transmitter. Then he wonders about Kirk's uniform and he starts to list Kirk's offenses, threatening to lock him up for 200 years. Kirk ruefully comments that that ought to be just about right (to return him to his own era).

Back in orbit, Spock and Christopher hypothesize in the Enterprises briefing room as to the captain's most probable situation, as they are planning a rescue operation. However, Christopher insists on coming down with them, to which Spock reluctantly agrees. He issues phasers only to himself and Sulu, set on maximum stun. They beam down, as the security policeman who beamed up earlier is amazed. Kyle offers the guard some chicken soup from a food synthesizer to satisfy his hunger, which only amazes him more. On the surface, Spock takes out the two guards holding Kirk, and frees him. However, while Kirk and Sulu talk, Christopher gets one of the security guard's guns. He holds it to Kirk, refusing to be beamed back up.

Act Four

Kirk tries to talk Christopher out of it, but he doesn't listen. He asks Spock to come out of Colonel Fellini's office, but as he moves towards Kirk, Spock comes up from behind, and administers a nerve pinch. He had suspected Christopher's actions, and had beamed into location for incapacitating Christopher. Sulu then beams up all four officers.

"Captain's log, Stardate 3114.1, subjective time: We must make an attempt to break free of this time or we and our reluctant passengers will remain its prisoners. All we have is a theory and a few facts."

Mr. Spock says that the best possible course of action is to use a slingshot effect like the one they used to arrive in the first place. Theoretically, the whiplash from the sun's gravity would send them into another time warp. At this point, Christopher asks what they will be doing about him and the guard. Spock states that for a moment, they will go into the relative past, and transport both the captain and the guard to points before they were beamed up. The events, though still in their minds, will not have occurred, so there would be nothing for them to report. Scott now brings up one problem. The Enterprise may not have enough braking control to stop in their own time. They may overshoot their century, or be torn apart. In other words, it won't be an easy ride.

Everyone assumes stations, as the Enterprise prepares for the time-warp. They leave Earth, and head towards the sun at warp factor 3. Christopher, at this point, tells Kirk how he always wanted to make it into space, and Kirk tells him that he made it farther than anyone in his century. As the Enterprise heads towards the sun, their warp factor increases, and the chronometers have started to move backwards. Christopher goes to put on his flight gear, and reports to the transporter room. As they approach the breakaway point, Sulu engages engines, and the ship is severely thrown. All power is just barely enough, but they do break free of the pull. As they head away from the sun, they gain speed, and the chronometers begin to move forward. Christopher prepares to beam back to Earth, and thanks Kirk for the look ahead. As they approach Earth, they energize, beaming Christopher back into the plane cockpit. However, there is no longer any Enterprise in the sky. Christopher reports to Black Jack, marking down the Enterprise as another UFO. They then beam down the guard, but he too finds no unusual activity at the base.

As they approach their century, they have to begin braking, despite some risks. Kirk, being annoyed by Spock's countdown, asks him to just never mind. They begin braking, but the ship is thrown violently. Scott reports from engineering that the engines are buckling, but they manage to make a safe and complete stop. They hear the friendly voice of Starfleet control, and Kirk reports that the Enterprise is home.

Log entries 
 Captain's log, USS Enterprise (NCC-1701), 2267

Memorable quotes
"I never have believed in little green men."
"Neither have I."
- Christopher and Spock, in their first encounter

"Don't touch anything, but I think you'll find it interesting."
"Interesting is a word and a half for it, Captain."
- Kirk and Christopher, on the bridge

"Maybe I can't go home, but neither can you. You're as much a prisoner in time as I am."
- Christopher to Kirk, in the captain's quarters

"Now you're sounding like Spock."
"If you're going to get nasty, I'm going to leave."
- Kirk and McCoy, on retraining and re-educating Christopher for the future

"I made an error in my computations."
"Oh? This could be an historic occasion."
- Spock and McCoy, in sickbay

"Wait a minute. I don't have a son."
"You mean yet."
- Christopher and McCoy

"It is a fact, Doctor, that prowling by stealth is more time-consuming than a direct approach."
- Spock to McCoy, in the transporter room
 

"How did you get in?"
"I popped in out of thin air."
- Fellini and Kirk, during Kirk's interrogation

"What is that? Is that a uniform of some kind?"
"This little thing? Just something I slipped on."
- Fellini and Kirk, about the latter's uniform

"I am going to lock you up for two hundred YEARS!"
"That ought to be just about right."
- Fellini and Kirk

"Blast your theories and observations, Mr. Spock! What about Jim? He's down there alone, probably under arrest! He doesn't have a communicator and we can't locate him or beam him back aboard without one!"
"I am aware of that, doctor."
- McCoy and Spock, about Kirk

"Anyway we do it, it means a mighty rough ride."
 - Scott, on the slingshot effect

"Well gentlemen, we all have to take a chance… especially if one is all you have."
- Kirk, after being presented with the slingshot effect as the only option to return to the 23rd century

Background information

Production timeline
One-page synopsis by Robert Justman: 
Story outline by D.C. Fontana: 
Revised story outline: 
First draft teleplay by Fontana: 
Second draft teleplay: 
Final draft teleplay by Gene L. Coon: 
 Additional revisions: , 
Filmed:  – 
Day 1 – , Monday – Desilu Stage 9: Int. Bridge
Day 2 – , Tuesday – Desilu Stage 9: Int. Bridge, Transporter room
Day 3 – , Wednesday – Desilu Stage 9: Int. Corridors, Turbolift, Sickbay, Kirk's quarters
Day 4 – , Thursday – Desilu Stage 9: Int. Kirk's quarters, Briefing room, Engineering
Day 5 – , Friday – Desilu Stage 10: Int. Air base corridor, Records section, Security office
Day 6 – , Monday – Desilu Stage 10: Int. Jet cockpit, Photo lab, Dark room, Radar room
Original airdate: 
Rerun airdate: 
First UK airdate:

Story
The episode originated from a one-page story synopsis associate producer Robert Justman submitted to Gene Roddenberry for possible consideration. Although almost beat for beat, Justman's proposed story is the same as this episode, Roddenberry never acknowledged Justman as the source or paid any royalties to him for the idea. (Inside Star Trek: The Real Story, pp. 133-137)
This episode was originally going to be the second part of a two part story that would have begun in . In an earlier draft of the script, when Kirk ordered a hyperbolic course, he wanted the direction to be "Doesn't matter… the way we came… toward Earth."

Props and costumes
Matt Jefferies designed the trophy with the soaring jet aircraft, seen in the case on the air base. 
The small scanning device that Kirk uses to unlock the Omaha base computer-room door appears to be the same one used by Scott and Joe Tormolen in , and by Richard Daystrom in .
 Actor Roger Perry liked his Starfleet uniform so much, he asked DeForest Kelley if he could take the shirt home. Kelley replied, "Well, they frown upon that. But you could possibly just stick it into your bag, and nobody's going to say anything." Perry decided not to do that, but after seeing the eventual success and legacy of Star Trek, he regretted he didn't take the shirt home. (These Are the Voyages: TOS Season One, p. 428)

Effects

The opening screenshot was actually taken at Georges Air Force Base California. It shows F-104C Starfighter, AF Ser. No. 57-0914, 435 TFS, 1965. This aircraft was deployed to Ubon RTAFB, Thailand in 1966 and assigned to 8 TFW. It crashed due to engine failure over Thailand on 16 January 1967. 
Footage of the Earth (going closer and further, inside the atmosphere) on the Enterprise viewscreen is reused from .
The music played as Christopher observes the ears on Spock, heard in its entirety in , was written by composer Joseph Mullendore during his scoring for , but it went unused at that time. It is an uptempo version of the closing theme for the show. Mullendore had also arranged the "lounge" version of the theme for the same episode, also heard in . 
This is the only episode to end on a close up of George Takei before the final Enterprise flyaway.

Continuity
This is the first episode where the Enterprise visits Earth during its five-year mission.
 Kirk's assertion that there are only twelve starships like the Enterprise in the fleet is contradicted in The Making of Star Trek, p. 165, by Gene Roddenberry and Stephen E. Whitfield, which lists the names of fourteen starships, though on the same page the starship Farragut is described as destroyed, and its fate would already be known at this point in the series. This leaves Kirk's statement technically correct with the Enterprise and the other twelve like it still in service (The fate of the Valiant would not be revealed to Starfleet for another two episodes).
Except for the 6 am launch time for Apollo 11, which actually was 9:32 am on Wednesday July 16, 1969, the writer of this episode, D.C. Fontana, correctly predicted the day of the week.
The events of this episode, which take place in 1969, occurred over a year after those of , which take place in 1968.
This is the last episode in which Spock's rank is stated as lieutenant commander.
Though Spock tells Sulu to issue phasers for both himself and Spock when they return to the Air Force base to retrieve Kirk, only Sulu is shown armed with a phaser in the transporter room.
This episode establishes the presence of a quartermaster on board the Enterprise. Kirk said to Spock (referring to Captain Christopher), "Why don't you have the quartermaster issue him something more suitable?"
Kirk tells Captain Christopher that the Enterprise operates under the authority of the "United Earth Space Probe Agency," which Kirk describes as a "combined service" when Christopher presumes that the Enterprise is operated by the navy. Along with Kirk's log entry reference to "UESPA" in , this is the only time in the original series that this authority is mentioned. In the Star Trek Concordance, author Bjo Trimble suggests that it is a fictional name, designed to keep Capt. Christopher in the dark about the true nature of the Federation. The name would be established canonically as being the agency under whose authority the United Earth Starfleet operated under in .
This episode is the first of two episodes to have a food synthesizer in the transporter room. According to D.C. Fontana, budgetary restrictions precluded taking the security police sergeant to a dining facility or having another actor in the scene bring him food, so Kyle was employed to provide the sergeant's chicken soup from the dispenser. (The World of Star Trek, 3rd ed., p. 40)
This is one of many episodes to contribute to the ambiguous future timeframe of the Original Series. When Fellini threatens to lock Kirk up for two hundred years, Kirk lightly notes that "That should be just about right." Two hundred years from that point would be 2169, the mid to late 22nd century. The original series is established to be set in the late 2260s.

Remastered information

The remastered version of "Tomorrow is Yesterday" aired in many North American markets during the weekend of . The episode was heavy in new effects, with revamped CG shots of Earth from orbit – based on NASA space shuttle photographs – as well as new CGI shots of Captain Christopher's jet fighter, the Enterprise falling into Earth's atmosphere, and an all-new sequence depicting the slingshot around the sun.

Video and DVD releases
Original US Betamax release: 
UK VHS release (two-episode tapes, CIC Video): Volume 12, catalog number VHR 2305, release date unknown
US VHS release: 
UK re-release (three-episode tapes, CIC Video): Volume 1.8, 
Original US DVD release (single-disc): Volume 11, 
As part of the TOS Season 1 DVD collection
As part of the Star Trek: Fan Collective - Time Travel DVD collection
As part of the TOS Season 1 HD DVD collection
As part of the TOS Season 1 Blu-ray collection

Apocrypha
 This episode (or more accurately its stardate of 3113) was used as the basis for the "origin" of material that was published as the Star Fleet Technical Manual; the first pages of this manual explain how this occurred.
The second issue of John Byrne's Assignment: Earth series, "Yesterday, Today and Tomorrow", tells the story of Gary Seven's role in the events of this episode.

Links and references

Starring
William Shatner as Kirk
Leonard Nimoy as Spock

Also Starring 
Roger Perry as Major [sic] Christopher

Featuring
DeForest Kelley as Dr. McCoy
 Hal Lynch as Air Police Sergeant
Richard Merrifield as 
John Winston as Transporter Chief
And
Ed Peck as Colonel Fellini

With
James Doohan as Scott
George Takei as Sulu
Nichelle Nichols as Uhura
Mark Dempsey as Air Force Captain
Jim Spencer as Air Policeman
Sherri Townsend as Crew Woman

Uncredited Co-Stars
Majel Barrett as Computer Voice
 William Blackburn as Hadley
John Burnside as Air policeman #2
 Frank da Vinci as Brent
Eddie Paskey as Leslie
 Unknown actors as
Bobby
Radio announcer (voice)
US 498th Airbase personnel
Enterprise lieutenant/navigator
Enterprise security chief (voice)
Air Force guard

References
1954; 1968; 1969; 2217; .38 police special; US 498th Airbase Group; accident; ADC Control; ; aircraft; Air Defense Command; airman (aka airman basic); Air Police; alarm; all decks alert; "all right"; "all the time"; Alpha Centauri; altitude; AM; answer; Apollo 11; area; arrest; astronaut; atmosphere; audio; authority; automatic helm setting; auxiliary power; B-52 Stratofortress; bag; belt; blackjack; black star; blip; Bluejay 4; braking power; buckling; burglary; calculation; camera; Cape Kennedy; "carry on"; casualty report; chance; choice; chicken soup; ; Christopher's wife and daughters; chronometer; cloud cover; cockpit; computer; computer check; computer system; coordinates; countdown; Cygnet XIV; cylindrical; damage control party; darkroom; deck; ; ; drawing; duty bound; Earth; Earth-Saturn probe; Eastern Standard Time; emergency signal; Engineering Officer; English language; ; escape velocity; espionage; evidence; F-104 Starfighter; F-105 Thunderchief; fact; film (material); flight suit; fool; friend; g; girlfriend; guest; hand; historical tape; horse; hour; idea; identification; impulse power; "in case"; industry; injury; interceptor; interrogation room; jet; joke; jury rig; landing party; liar; little green man; logic; Luna; magnetic tape; ; maintenance note; ; matriarchy; ; mind; minute; mirage; missile; museum; name; NASA; nation; Nebraska; nuclear warhead; Omaha; orbit; "over my dead body"; passenger; personality; photography; photo lab; physical training; place; plane; Pluto; ; prisoner; problem; progress report; quartermaster; RADAR; radio; record computer; record section; risk; rubber band; sabotage; Saturn; search party; second; secondary system; sector; ; security section; signal; sky; slingshot effect; Sol; space; speed; serial number; staff sergeant; starbase; Starbase 9; Starfleet channel; Starfleet Control; Statistical services division; Strategic Air Command; stock; sun dog; thing; theory; thousand; time warp; time zone; tractor beam; transmission; transporter; transporter chief; transporter room; truck; unauthorized entry; "under arrest"; uniform; United Earth; United Earth Space Probe Agency; UFO; USAF; US Navy; variable; visual contact; Vulcan neck pinch; warp power; weather balloon; Wednesday; week; wing; word

External links

de:Morgen ist Gestern
es:Tomorrow is Yesterday
fr:Tomorrow is Yesterday (épisode)
ja:宇宙暦元年7・21（エピソード）
nl:Tomorrow is Yesterday
pl:Tomorrow is Yesterday
sv:Tomorrow Is Yesterday
TOS episodes