Time Travel Tense Trouble

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"Can we get some food? I haven't eaten since later this afternoon." —Aaron, Primer

Most Indo-European languages have multiple tenses, to differentiate things that have happened from things that will happen, plus some to define what had happened before that, not to mention some that are a bit less identifiable in their everyday uses (I'm looking at you, Pluperfect Subjunctive). It mostly works fine when your timeline is a strict progression from cause to effect.

Unfortunately, when you are watching the San Dimas Time, winding through the threads of the Timey-Wimey Ball, chasing another time traveler who is always one step ahead of you, it can become awkward. As a result, time travelers will often stumble over their wording, leading to use of tenses that can be torturous to understand.

Usually this is an experienced traveler explaining in eloquent yet incomprehensible terms that they didn't "just succeed", when you return from an adventure in the future. Alternatively, a less experienced character will attempt to explain what's going on, and struggle with their terms.

If your Future Me shows up, there may be pronoun trouble on a similar style, especially if there's several versions of future characters knocking around.

This is related to Meanwhile in the Future, Anachronic Order.

Examples of Time Travel Tense Trouble include:

Anime and Manga

• Mikuru from Suzumiya Haruhi is aware of the tense trouble, but she keeps flubbing it anyway. Considering that Mikuru is spacey and Moe Moe, this leads to Adult!Mikuru showing Kyon a mole on her breasts while saying something like "But you were the one who told me about it...wait, has that not happened yet? oops...". Later in that episode Kyon casually asks Mikuru if she has a mole "right about here" and points to the location on his own chest. She turns around, checks, and starts trying to beat the information out of him. That would be where Kyon "told her about it"- it's a paradox.

Boardgames

• In Time Agent the objective is to have always been winning by using time travel to have changed the past, while never having had time travel invented. The flow of causality operates according to the Schrödinger's Gun trope, which means that technologies often work until you discover that even before you had been making changes to the timeline, they had never been working. In one instance the player commander of the Zytal had to leave and be replaced by another player, but from the board's perspective, the new player had always been the commander of the Zytal, for the previous commander had never been playing.

Comic Books

• In Watchmen, Dr. Manhattan, who is able to perceive the past, present and future, says "Yes, yes, he killed Blake and half of New York. Excuse me, Rorschach, I'm informing Laurie 90 seconds ago," to Laurie "Silk Spectre" Juspeczyk, being confused by tachyon interference, before saying the same thing to Rorschach 90 seconds later. He's even in the exact same pose and position (relative to the walls of the panel) both times he says it.
  • That, and the whole flashback (flashnow?) scene on Mars.
• In a Uncle Scrooge story, the evil witch, Magica has this problem

Magica: This is like all the times in the past that Scrooge himself has chased me in the future. I mean... what am I talking about?

• A frequent out-of-universe problem when trying to describe events crossing Crisis on Infinite Earths, due to the major differences in how the retcon affected different characters and different past events. A few characters were rebooted as completely new characters (Wonder Woman), some were made so that they had been around before the Crisis, but their personalities and histories suddenly had always been very different from what all previous comics portrayed (Superman), and some had basically the same history and memory that they had had before the Crisis (The Flash, Green Lantern). Therefore, there's both the reader's perception of what "Pre-Crisis" and "Post-Crisis" means (Pre-Crisis: Silver- and Bronze Age, Post-Crisis: Dark- and Modern Age), and there's the characters' perception of what "Pre Crisis" and "Post Crisis" means (basically: Pre Crisis: Before Barry died, Post Crisis: after Barry died). This leads to descriptions like "After the Crisis, Batman changed so that he had been dark and brooding both before and after Barry died."
  • Also, Barry's life, career and friendship with other characters, as well as the vague event that caused his death, are all perfectly compatible (as far as their memories are concerned) with their personal histories and timelines that had been established after the Crisis was written. So basically, the characters can all recall and talk about events that as far as they are concerned, occurred when Barry Allen was still alive, but most of those events are significantly different from how they were reported by comic books written before the Crisis was published.
• The Invisibles sometimes shows events taking place outside of time, where not only tenses suffer but the entire linear construction of sentences. One such nonlinear word balloon might contain the words "From" "look" "at" "you" "are" "in" and "allnow", to be arranged by the reader in whatever order they need.

Fan Works

• In Hogyoku Ex Machina:

Ichigo: Hinamori? They were pretty close, right? Matsumoto: Were? Ichigo: Are. Sorry. She got… will get better.

• In Here Be Dragons:

Syaoran: Please don't get too upset at my past self for the things he is going to do, he's going to be going through a very hard time just then.

Film

• The tagliney prophecy which drives the action of the animated Science Fiction film Light Years makes use of it: "In a thousand years, Gandahar was destroyed. A thousand years ago, Gandahar will be saved."
• Back to The Future Part II has something like this:

Marty: It's my fault — the whole thing is my fault. If I hadn't bought that damn book, then none of this would've happened. Doc: Well, it's all in the past. Marty: You mean the future. Doc: Whatever!

• One of the best known Narms of Plan 9 from Outer Space is that the narrator, a fortune teller, switches frequently between the past, present and future tense while describing his prophecy:

Criswell: Future events such as these will affect you in the future... And now, for the first time, we are bringing to you the full story of what happened on that fateful day.

• In Star Trek IV: The Voyage Home, Gillian catches Spock referring to the extinction of whales in the past tense.
• Page quote for Primer. "I haven't eaten since later this afternoon."
• A consistent element of the Terminator series (although rarely lampshaded), going back Sarah's quote from the first movie: "You're talking about things I haven't done yet in the past tense."
• Played with in the Dark Knight Riff Trax:

Gordon: We've found his next target. He's put it in tomorrow's newspaper. Kevin: Then we'd have been too late. If only there will be something we could do.

Literature

• In Harry Potter, Hermione insists on the correct tense when she travels back in time.
  • Hermione likes things just right!
• The Hitchhiker's Guide to the Galaxy has a good excerpt on the mechanics of time travel useful for this. There's even a book written In-Universe called the Time Traveler's Handbook of 1001 Tense Formations by Dr. Dan Streetmentioner. However, the book has been described as "an exceptionally dull read", and most readers only get as far as the section on the Future Semiconditionally Modified Subinverted Subjunctive Intentional before giving up. Because of this, in later editions of the book all pages beyond this point have been left blank to save on printing costs, which will turn out to be is going to be discovered to have been is probably, at some point, sooner, later or before, going to be Hilarious in Hindsight... or something...
  • Note that the titular Guide doesn't even bother trying to explain the tenses, and simply notes that it does not use the future perfect tense, because it was discovered not to be.
  • There is also an excerpt from Mostly Harmless that goes (and try to wrap your mind around this one, now): Anything that happens, happens. Anything that, in happening, cause something else to happen, causes something else to happen. Anything that, in happening, causes itself to happen again, happens again. It doesn't necessarily do it in chronological order though.
• Discworld:
  • The Discworld Companion entry for a character existing in a Stable Time Loop says "Dios was (or is, or will be - certain temporal uncertainties make the choice of tense very difficult)".
  • But when Vimes goes back thirty years in Night Watch, he is told to "just imagine things happening one after another" and sticks with that as less confusing.
  • Also, in Equal Rites, when it is explained that the dead are unbound from all dimensions, the narrator describes the fact that a cat appears to simultaneously be its own age, a newborn kitten, and a decrepit moggy, as resembling a kind of white, cat-shaped carrot, "which will have to suffice until someone is able to devise effective fourth-dimensional adjectives".
  • Reaper Man:

And at the end of all stories Azrael, who knew the secret, thought: I REMEMBER WHEN ALL THIS WILL BE AGAIN.

• Averted in Poul Anderson's series of short stories about the Time Patrol. In those stories, the Patrol developed an artificial language, called Temporal, which allowed Patrolmen to discuss such matters without any of the tense problems raised in this trope. Since only Time Patrolmen learned and used Temporal, it also served as a way that Patrolmen could speak between themselves without risk of being overheard (or more accurately, understood) by others.
• Shows up a few times in Harry Harrison's The Technicolor Time Machine.
• Larry Niven's stories involving Svetz love to play with this trope. Svetz's solution to a time paradox involving the destruction of Ford's Model-T demonstrates very well how bad English is with time travel:

Svetz: "Maybe we can go around you. Zeera, try this. Send me back to an hour before the earlier Zeera arrives. Ford's automobile won't have disappeared yet. I'll duplicate it, duplicate the duplicate, take the reversed duplicate and the original past you in the big extension cage. That leaves you to destroy the duplicate instead of the original. I reappear after you've gone, leave the original automobile for Ford, and come back here with the reversed duplicate. How's that?" Zeera: "It sounded great Would you mind going through it again?" Svetz: "Let's see. I go back to-"

• In Paradox in Oz by Edward Einhorn (1999), Ozma travels in time with the assistance of a Parrot-Ox, and finds out that there are two kinds of time she can travel in: "Oz time" and "Ozma time", the former being travel through the timeline of the entire land of Oz, while the latter is travel within her own personal timeline (letting her undo things she did, including other time-traveling).
• The Narnia Time in effect between the territories in The Pendragon Adventure occasionally causes this sort of trouble. Usually involving rookie Travelers (We're looking at you, Spader and Siry).
• Johnny and The Bomb has a few instances of this when everyone's back in 1941.

"There's an old windmill up there. It was some kind of look-out post during the war. Is, I mean."

• The Gospel of John in The Bible has a nice bit of Mind Screw as Jesus says “before Abraham was born, I am!” This is a statement of divinity instead of evidence for a time-travelling Jesusmobile, but omnipresence is just as messed up.
  • The phrase "I am" may be related to Yahwei or Jehovah, based on what God told Moses: "I am that I am."
  • The Bible also tends to record prophesies as though the future events they describe have already happened.
• In the Young Wizards series it's mentioned in passing that the Speech, the Language of Magic with which reality was written, does have the words to deal with thing like this, including talking about something in the past which used to be but no longer is due to the past having been changed.
  • Also, in the Book of Night with Moon (another novel in the same universe) Arhu, a visionary, says, " Au, Rhiow, the way we talk about time doesn't work for talking about vision. I need new words or something!" Presumably he has not learned enough of the Speech yet.
• Referenced in a Star Trek Expanded Universe novel about the Department of Temporal Investigations, which deals heavily with the logic and philosophy behind this trope. It concludes that the simplest solution is to look at things from the perspective of someone outside time and pretend everything is happening at once, and as such simply use present tense for everything.
• Due to the non-linear narrative structure of The Illuminatus Trilogy, this happens with the narrator, who is aware of the non-linearity. As the book goes on, several of the characters fall victim to this trope after becoming effectively Unstuck in Time.
• Time Scout makes this easy. It's running on a lot of different San Dimas Time portals to the past. If a portal leads to 1888 and the time travellers are talking about an event in 1889, they use the future tense. When they're talking about the future/present, they just use the present tense.
• Dracula and Bathory suffer from this as children in Count and Countess.

Live Action TV

• In the Red Dwarf episode "Future Echoes":

Lister: Hey, it hasn't happened, has it? It has "will have going to have happened" happened, but it hasn't actually "happened" happened yet, actually. Rimmer: Poppycock! It will be happened; it shall be going to be happening; it will be was an event that could will have been taken place in the future. Simple as that. Your bucket's been kicked, baby.

• • After being erased by the inquisitor:

Lister: We don't exist here anymore! Kryten: Actually sir, we don't ever have existed here anymore, but this is hardly the time to be conjugating temporal verbs in the past impossible never tense!

• • • Truth in Television: the tenses were so difficult that Robert Llewellyn, playing Kryten, kept flubbing the line and eventually had to have a cue-card held up out of shot.
      • ...and then the line was cut anyway. It only resurfaced as they showed the final correct take after all the bloopers in the Smeg Ups collection.
• In the Doctor Who story "The Two Doctors", the Sixth Doctor comments on the Second Doctor in this convoluted way.

Sixth Doctor: Your Doctor is an antediluvian fogey! Allowing himself to be captured by the Sontarans. If anything happens to me as a result of it, I shall never forgive himself. Peri: Oh, I do wish you'd stop switching personal pronouns!

• • Dead Ringers featured "Christmas Day with Doctor Who"

Seventh Doctor: An anti-gravitation matter transmitter. Didn't you give me this next year?

• • In "The Beast Below," Amy ends up encountering the Time Travel Tense Trouble, telling a little girl she's getting married "a long time ago tomorrow morning."
  • In "The Vampires of Venice" Rory says he's getting married in 430 years...which is why they have to have this conversation RIGHT NOW.
  • Also in "The Vampires of Venice": The Doctor says the girls are like Houdini "He was shorter. Will be shorter. I'm rambling..."
  • And in the short comic relief specials "Space" and "Time"; Rory and Amy get to meet their past (future?) selves, and get confused when explaining that the Doctor told will tell them to go back, to tell themselves this, in order to make a Stable Time Loop.
  • And finally, a non-comedic use. Rose, in 'The Parting of the Ways', is sent back home to avoid a bloodbath taking place in the future. Jackie brushes it off, but it tears Rose up enough she tears up other things..
  • In the Eleventh Doctor episode "The Doctor's Wife," Idris!TARDIS in addition to liking biting (it's like kissing, only there's a winner!) has some initial trouble clarifying her tenses. It makes sense, since she's the spirit of the Doctor's vehicle trapped within a flesh body. She jumps across space and time without regard to those silly simian concepts of past, present, and future.
  • In Shada:

Chronotis: "I am, I was, I will be, Professor Chronotis. Oh dear... we Gallifreyans have never managed to come up with a satisfactory form of grammar to cover these situations.

• In Goodnight Sweetheart time traveler Gary Sparrow (who is married in the present day but is having an affair with a woman in 1940s Britain) upbraids his friend for cheating on his wife. When the obvious hypocrisy is pointed out to him, Gary replies "That's different. All my indiscretions are in the past. Even my future indiscretions are in the past.".
• Star Trek: Voyager in episode "Relativity":

Braxton: Thanks to you, we've learned that the temporal disruptor was and will be concealed here. I gave up trying to keep my tenses straight years ago.

Janeway: (returning to Voyager from the 29th Century) See you in the 24th Century. Seven of Nine: I look forward to it. Or should I say backward? Janeway: Don't start.

• • Captain Janeway will happily deal with negative space wedgies all day long, but she hates dealing with time travel for precisely this reason.
• Even happened on The Daily Show. "You're hurting my brain, Stephen."
• In Day Break, Brett often ran into this whenever he tried to explain the Groundhog Day Loop to another character.

Chad: When did I say this? Brett: Today. Chad: Wait, how many todays ago? Brett: Yesterday.

• Top Gear, when James May described a Saab, while wondering if Saab was going to go out of business before the show was broadcast:

"They say, or said, that it's based on a jet fighter, or was, but it isn't wasn't."

• The sisters (Prue in particular) in Charmed always run into difficulty when trying to get their heads around the concept of tenses when time travel is involved.

Prue: We barely got away as it was. ... Is. Will be. You know, I've never been good with tenses.

• Topical Panel Games like Have I Got News for You also get confused by tenses when describing something that might happen between recording and broadcast (and might have changed by the repeat. And heaven knows what'll be happening by the time it's on Dave...)
• Poked fun at on Mystery Science Theater 3000 when they were going through a time rift. Have you seen my chicken puppet?
• In an episode of Quantum Leap, Sam leaps into the past version of his friend and helper Al; early on, Al has a bit of tense trouble relating to his younger self ("I think I'm...I mean, he thinks I'm my uncle.") Eventually Sam suggests that they refer to Young Al as "Bingo", which was his Air Force callsign.

New Media

• From The Other Wiki's article on the MIT Time Traveler Convention: "The spacetime coordinates continue to be publicized prominently and indefinitely, so that future time travelers will be aware and have the opportunity to have attended."
• Parsley Boobs has this exchange between the future counterparts of Carl and Steve:

Steve: Close the door! Don't you know he suffers from amblyopia? Future Carl: Yes I do... for I are he! Only, I'm from the future. Future Steve: You know, I really do think it's "I AM he". Future Carl: It's all this time traveling! It really confuses me as to what tense we should be using!

Tabletop Games

• Continuum invents a time-travellers' jargon with terms regarding your personal 'spanner' timeline being separate from terms used in the general 'leveller' timeline. Things in your subjective past are in your "age", while things in your subjective future are in your "yet". When talking about objective time, things are either "Up" or "Down"; the year 2000, for example, is Up from the year 1990. All events except those in your personal past require the present tense, since in a second, they may be your "now" too.
• Averted in one place in GURPS Time-Travel by saying that there are two timelines for the adventurer, the time he came from "hometime" and the time he is adventuring in and Hometime keeps going while the adventurer was adventuring. Thus all that is necessary is to distinguish between home past and away past.
• Genius: The Transgression runs into this once it starts talking about time travel; when discussing the consequences of changing the past it says that "what used to happen (and here the past tense gets into a bit of trouble), is that you got your ass kicked by the transsapient gods who live at the end of time."

Video Games

• City of Heroes' Mender Lazarus has trouble with tenses. ("This doesn't make any sense to me. My readings tell me that your Temporal Scaling isn't strong enough yet to support the mission I had planned for you. But you've already done the mission. I know. I was there.")
  • Made even worse because he's also in contact with a nearly infinite number of alternate selves, some of whom passed the local universe's Do Not Pass Go, Do Not Exist time travel brick wall. To a lesser degree, Nemesis does this as well. Not due to time travel, but simply thanks to having plans upon plans upon plans.
• At the end of Final Fantasy:

Garland/Chaos: "Two thousand years from now, you killed me."

• Lampshaded, like everything else, in Kingdom of Loathing. At the beginning of time, all messages are prefaced by "you remember" followed by a past participle or past perfect; the Distant Past switches off between first-person present and third-person past (because you're inhabiting the memories of your ancestor) seemingly at random, and the exposition upon arriving in the future for the first time starts out in future tense before saying "You will then start getting your narrative in present tense, because it's the future, we get it, no need to run that joke into the ground."
• Naturally, Prince of Persia also falls victim to this trope during Sands of Time's final boss fight. Among the banter we find this: "It happened! ... Well, it will happen!" referring to the events of the game being experienced, rewound, and then about to happen (again?) if the Prince doesn't do something about it.
• The Achron fandom made a little of their own grammar to explain stuff in the game. They talk about game-time and real-time (also referred to as "time" and "metatime"), and refer to units and events as early or late. When they specify when something happened, they use an ordered pair for the time.
• A boss in Avernum 5 summons two future versions of himself to assist him, and he does his best to keep his grammar consistent when shouting orders to them. He loses track and starts rambling when you kill both future selves and screw up the timeline.
• The first Discworld game lets players go back and forth between the past and the present. If you try to use an item that needs to be used at that place but in a different time, Rincewind will say "Try again later. Or earlier."
• In The Longest Journey, one of the species April encounters in Arcadia perceives the timeline all at once, and so has a horrible time keeping tenses straight when speaking to more temporally limited creatures.
• The opening cutscene to Spider-Man Edge of Time. "Earlier...in the future."

Web Original

• Examined and refuted by Things of Interest in detail here.

Webcomics

• Irregular Webcomic has one here. Of course, Nazi scienc—wait, grammar sneers at it.
  • "When we will have done what we soon will do in die past, you will see the results of what we have now already will have done!"
• Related incident in 8-Bit Theater after Sarda does something to Berserker when he attacked him:

Cleric: I demand a rational explanation. Sarda: Your brain can't process six of the verb tenses needed to explain it to you.

• • More recently, again from Sarda: You can't do something you haven't yet done differently than how it will come to be done.
• A truly memorable example occurs in Bob and George, referencing Hitchhiker's Guide (the comic in question is indeed titled "Future Semiconditionally Modified Subinverted Plagal Past Subjunctive Intentional"), as Bob, trapped in the future, tries to find out from Prometheus/Protoman how he gets back to the present:

Bob: Okay, if I told you what I did, how did I get back? Prometheus: Don't you mean, if you will tell me what you will do, how will you get back? (Beat Panel.) Bob: How about, if you won't tell me how I did get back, I will shove my boot up your ass?

• In Schlock Mercenary, they give us both the pronoun trouble version, as well as the tense issue.
  • Also, due to versioning. When speaking about people who had their minds backed up and restored, there's sometimes a need for reference to the clones vs. the originals after their last backup. Attempts to express it in a natural language lead to phrases like this:^spoiler!

Neeka: You were to have been excellent as a co-worker.

• In Simulated Comic Product: Behold! the museum of the future!
• Described in The Rant for this Touhou Nekokayou, where it divides temporal conversation between "subjective" (what the time traveller personally experience), "objective" (chronological order), and "metatemporal" (the perspective of changes made to the timeline).
• In one Dinosaur Comic, T-Rex likes to assume every unknown historical figure is, in fact, himself on a time travel ("It sounds rad to me!")

Utahraptor: ...I see. So if I said that nobody knows who the historical King Arthur is? T-Rex: I'd say "that's me!" His exploits shall be going to have been being done by me! Utahraptor: Future perfect continuous passive? T-Rex: Ahem. Future perfect continuous passive, BITCHES.

• Narbonic: Dave, a long-time chain-smoker, travels back in time and alters the past so that he never started smoking. Later, when he mentions this, his co-workers give him odd looks and comment, "Dave, you never smoked."
  • Lampshaded, painted, and festooned with neon lights in the Director's Cut commentary. Loyal readers from the comic's first run, when they saw Dave smoking in the early strips, inevitably commented, "Say ... Dave never smoked!" "Yes, but he hasn't never smoked yet!" (The Director's Cut has finally reached the point where Dave has, at last, never smoked.)
• Homestuck: "But it looks like there's already been some action in here. Or there will be. You can never take tense for granted with these goons."
  • "It begins to dawn on you that everything you are about to do may prove to have been a colossal waste of time."
  • Thanks to the timebending properties of the Trolls' chat client, this is practically guaranteed in any conversation between the Trolls and Kids, or in the Trolls' memos.

FCG2: OK I'M SHUTTING THIS MEMO DOWN FOR MY PAST SELF. FCG2: SINCE HE'S CURRENTLY LYING UNCONSCIOUS ON THE FLOOR AN HOUR AGO. FCG2: SEE YOU IN THE FUTURE-NOW.

• This ^{[dead link]} Doctor Who parody from Scenes From A Multiverse features "That's OK, I'll try you again yesterday!"
• In this strip from the Doctor Who comic The Stalker of Norfolk, new companion Beverly attempts to talk about someone from her personal past.

Western Animation

• In Kim Possible: A Sitch in Time Shego's future self tries to explain her scheme to take over the world in the future to her present self.

Future Shego: Listen, we don't have a lot of time... OK, actually we do--well... we will. Present Shego: When you wanna make sense, just let me know. Future Shego: Grab the Time Monkey! Present Shego: Why? Future Shego: You need the Time Monkey. Present Shego: Can't I just use yours? Future Shego: No, this is mine! OK, well, actually, it's yours too, I mean... well it's the one you're supposed to steal, so technically... Present Shego: If you need me, I'm gonna be in there watching Kim Possible lose.

• • Later:

Kim Possible: But if the Supreme One has the time monkey in the future... or the past... or... Wow. Aah! Brain pain. Rufus 3000: Time travel does that.

• In the Futurama episode "The Farnsworth Parabox," an analogous situation arises while discussing parallel worlds. Professor Farnsworth exclaims, "Nonsense! I would never do such a thing unless you were already having been going to do that!"
  • In a scene parodying Minority Report, Fry's reaction when discovering he will commit a crime:

Fry: No, no! What have I will have done?

• South Park had the memorable episode "My Future Self and Me", where Stan's adult future self (later revealed as an actor) comes to live with present, young Stan. "Don't be so hard on yourself, Stan" and "Why don't you go upstairs and play with yourself?"
• In this scene from the Teenage Mutant Ninja Turtles 2003 episode "Timing Is Everything", the Turtles receive a message from their future selves, as well as a reminder to send the message to their past selves when they will have reached that point in the future.
• Paradox from Ben 10 Alien Force has this problem; more specifically, it's the fact he seems to mix up events that haven't happened yet with events that have.

Paradox: (to Ben) You're much smarter now than when I first met you later.

• Ditto for Clockwork on Danny Phantom:

Clockwork: I sent him back to his own time... or should I say, forward to his own time? You see, for me, time moves backwards, and forwards, and... oh, why am I bothering? You're fourteen.

• My Little Pony Friendship Is Magic, "It's About Time": Twilight Sparkle receives a message from herself a week in the future, and the state of her future self (wearing a torn black jumpsuit, her mane all messed up, and with an eyepatch and a scar on her cheek) causes her to worry: "What a mess she is. Or I am... or will be!" It turns out her future self was trying to tell her not to panic (which caused her to panic anyway). After she goes back in time to try and deliver her original message, she realizes what just happened and says "Now I'm going to have to worry for a whole week!" despite the fact that for her the ordeal has passed.

Real Life

• Microsoft Outlook's "Warning: This meeting occurs in the past."
• Subversion's error message "Cannot reverse-merge a range from a path's own future history".
• Larry Niven called this effect "Excedrin Headache Number SQRT(-π)".
• Of course, this problem affects only languages with compulsory tense-marking.
• This is part of why explaining time modeled as the 4th dimension can be quite difficult.