History Main / PortalToThePast

* First, Second, and Third Earth (past, present and future) in the ''Literature/{{Pendragon}}'' series are linked by the PortalNetwork, and employ SanDimasTime.

* The whole ''Series/MirrorMirror'' New Zealand TV series was built upon this trope, resolving around a magical mirror that can send people back and forth between 1919 and 1995. There are a few conditions; the mirror only works as long as it is in the exact same position in both eras, and it doesn't work for people/objects that already exist in the time period they try to travel to.
* Hordes of these show up in ''Series/{{Primeval}}'' where they make up the shows premise. They're called Time Anomalies by the cast.

*** In its second canon appearance, on ''Series/StarTrekDiscovery'', the Guardian (masquerading as a human named Carl) opens a door for Philippa Georgiou that not only leads over 900 years into the past, but also to the MirrorUniverse, where she appears in her Terran Emperor regalia. It may not have been the same Mirror Universe, though, as Georgiou was able to affect changes in it and then returned after dying. From Burnham's perspective, it took only a moment. But Georgiou's bioscanner recorded three months' worth of data in that moment.

* In ''Film/MightyMorphinPowerRangersOnceAndAlways'', Robo-Rita, the evil essence of Rita Repulsa [[spoiler:in Alpha-8's body]], kidnaps various Rangers to power a device to open a portal back in time to 1993, when the Evil Space Aliens' dumpster is accidentally unsealed, so the original Rita can conquer Earth unopposed by killing the original Mighty Morphin Power Rangers before the team is ever formed.

* The door to the Timeless River within Disney Castle functions as this in ''VideoGame/KingdomHeartsII''.

** One is featured in the ''Series/StarTrekStrangeNewWorlds'' crossover episode "[[Recap/StarTrekStrangeNewWorldsS2E07ThoseOldScientists Those Old Scientists]]" where Ensigns Brad Boimler and Beckett Mariner from ''WesternAnimation/StarTrekLowerDecks''' - set 120 years in the future of ''Strange New Worlds'' use it to travel back in time (Boimler in an accident, then Mariner a little while later in a failed rescue attempt). The episode features the cast of ''Strange New Worlds'' trying to figure out a way to get both ensigns back to their home time.

** One is feature in the ''Series/StarTrekStrangeNewWorlds'' crossover episode "[[Recap/StarTrekStrangeNewWorldsS2E07ThoseOldScientists Those Old Scientists" where Ensigns Brad Boimler and Beckett Mariner from ''WesternAnimation/StarTrekLowerDecks''' - set 120 years in the future of ''Strange New Worlds'' use it to travel back in time (Boimler in an accident, then Mariner a little while later in a failed rescue attempt). The episode features the cast of ''Strange New Worlds'' trying to figure out a way to get both ensigns back to their home time.

* In ''Manga/ShinobiLife'' the portal is in a lake in [[{{Ninja}} Kagetora's]] time, and connects to one above a skyscraper in the modern day. We later learn that [[spoiler: there is another portal from the modern day to the future, which Beni's mother often used]].

* Stone circles work this way in the ''Literature/{{Outlander}}'' book series-- but travel is really only ever something like "safe" if you have a certain assortment of precious stones with you, and it's got a very high fatality rate. (And as the heroine muses, the separation in the various times is roughly 200 years... just like in the folktales.)

* Creator/MichaelCrichton's ''Literature/{{Timeline}}'' has a wormhole that was accidentally discovered during a teleportation experiment. The wormholes leads to the past, specifically, to France in 1357[[note]]Actually it's not the past - the novel makes a big point that it's not time travel, TheMovie on the other hand straight up calls it time travel. It's in fact a parallel universe who's time exists concurrent with ours, but is desynced so that its present is our 1357. Further, due to the quantum nature of universes, events in 1 are duplicated in all others. Hence a pair of glasses left in a universe where it's 1357 must also exist in the same place in a universe where it's 2001.[[/note]]. The events in the present and the past are synced, although it's also implied that YouAlreadyChangedThePast (i.e. no changes in the timeline are possible). When the quantum mirror is damaged by a grenade, the lead technician fears the connection may be lost for good, as they have no idea how the link works.

* The comedy ''Series/GoodnightSweetheart'' had the main character walking down an old cobbled street that would take him - and only him - back in time, where he fell in love with a World War II barmaid and committed time-travelling bigamy. Turns out it was due to the "harmonics" of time, and other characters could time travel but none of the main characters.

* ''Series/QuantumLeap'' works like this from Al's point of view - the door that takes him to Sam is synced up so that if Al goes away to do something for five minutes, Sam will have to wait out those five minutes before he returns. One episode has changes that take place instantaneously from Sam and Al's viewpoint. Specifically, the episode has Sam and Al switch places due to a lightning strike. Mistaking this for a radiation spike, the Quantum Leap computer blocks the door to the holo-room. So Al has to send a letter to their future colleagues with a request to deliver at a specific point in time. As soon as he drops the letter into the mailbox, the door opens. Interestingly, this synchronization only applies after Sam arrives, replacing someone. The leaps themselves are instantaneous from Sam's (and the audience's) point of view, but appears to take a random amount of time in the future, often several days.

* The ''VideoGame/StarOcean'' series has a planet specifically dedicated to a portal to the past: planet [[WhatDoYouMeanItsNotSymbolic Styx]]. It's used about thirty minutes into ''VideoGame/StarOceanFirstDeparture'', mentioned in ''[[VideoGame/StarOceanTheSecondStory The Second Story]]'', and used in ''[[VideoGame/StarOceanTillTheEndOfTime Till the End of Time]]'' to [[spoiler: contact the 4th dimensional beings that observe our MMO universe. That's right! We're all game characters that got ''pissed'' and came ''out of the computer'' to tell our creators to ''knock it off''.]]

* The protagonist of ''VisualNovel/TimeHollow'' has the ability to open these using his "Hollow Pen". He's not the only one, and any changes made by one Pen user cause "flashbacks" in others, giving them new places and times to open holes. Indeed, the BigBad changing things shortly after Ethan gets his Pen is what starts the whole plot. [[spoiler: And it turns out that anyone who steps through them will be removed from the flow of time, stopping them from aging from then on.]]

* ''WesternAnimation/TheOwlHouse'' has Time Pools, randomly-appearing puddles of liquid which can transport someone to another time period. Luz and Lilith use one to go back to the 1600s and meet Philip Wittebane [[spoiler: aka young [[BigBad Emperor Belos]].]]

* This appears to happen briefly within the first couple strips of Webcomic/GirlGenius. The story hasn't caught up the wherever the future end was, though, so we can't be sure.

* ''Series/QuantumLeap'' worked rather like this from Al's point of view - the door that took him to Sam was synced up so that if Al went away to do something for five minutes, Sam would have to wait out those five minutes before he returned.
** One episode had changes that took place instantaneously from Sam and Al's viewpoint. Specifically, the episode had Sam and Al switch places due to a lightning strike. Mistaking this for a radiation spike, the Quantum Leap computer blocked the door to the holo-room. So Al had to send a letter to their future colleagues with a request to deliver at a specific point in time (see ''Film/BackToTheFuturePartII''). As soon as he dropped the letter into the mailbox, the door opened.
** Interestingly, this synchronization only applied after Sam arrived, replacing someone. The leaps themselves were instantaneous from Sam's (and the audience's) point of view, but appeared to take a random amount of time in the future, often several days.

* The ''VideoGame/StarOcean'' series has a planet specifically dedicated to a PortalToThePast: planet [[WhatDoYouMeanItsNotSymbolic Styx]]. It's used about thirty minutes into ''VideoGame/StarOceanFirstDeparture'', mentioned in ''[[VideoGame/StarOceanTheSecondStory The Second Story]]'', and used in ''[[VideoGame/StarOceanTillTheEndOfTime Till the End of Time]]'' to [[spoiler: contact the 4th dimensional beings that observe our MMO universe. That's right! We're all game characters that got ''pissed'' and came ''out of the computer'' to tell our creators to ''knock it off''.]]

** One episode had changes that took place instantaneously from Sam and Al's viewpoint. Specifically, the episode had Sam and Al switch places due to a lightning strike. Mistaking this for a radiation spike, the Quantum Leap computer blocked the door to the holo-room. So Al had to send a letter to their future colleagues with a request to deliver at a specific point in time (see ''Film/BackToTheFuture''). As soon as he dropped the letter into the mailbox, the door opened.

* The Jumplink system in ''Film/TheTomorrowWar''.

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* ''Videogame/TheLegendOfZelda'':

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[[folder:Film]]

* ''Manga/InuYasha'': The Bone Eaters' Well connects the two time periods in sync, so that time flows at the same rate on both sides.

* The ''Series/RedDwarf'' episode "Stasis Leak" revolves around one of these. Lister wants to use it to save Kochanski; Rimmer wants to use it to save himself.

* ''Franchise/StarTrek''
** ''Series/{{Star Trek|The Original Series}}'' had the Guardian of Forever in the original series episode "The City on the Edge of Forever" (pictured). Kirk apparently assumed that the Guardian worked on SanDimasTime (leaving orders for the rest of the landing party to go back through the portal when Scotty decided he'd waited long enough), but it turned out not to (when he returned, Scotty said that he'd only "left a moment ago").

** An early ''Series/StarTrekVoyager'' episode had Harry Kim discover a wormhole that led back to the Alpha Quadrant. Only trouble was, not only did it come out in Romulan territory, but [[spoiler:Romulan territory twenty years earlier]]. May be TruthInTelevision: see RealLife below.
** ''Series/StarTrekDeepSpaceNine'' episode "Time's Orphan" has O'Brien's daughter Molly fall through one. They manage to pull her back, but their instruments are a bit off and they pull her out ten years after she had gone through. Later, they let the now-feral Molly [[spoiler:return "home" through the portal (which she's known for even longer than she'd known her family in her childhood), only to come across her 8-year-old self having just come through the portal the first time, allowing her to rescue herself in her own past. Or at least one version of herself.]]

* [=TRAX=], the time machine of ''Series/TimeTrax'' could only send its subjects approximately 200 years into the past.
** The show is inconsistent with its time travel. Some episodes claim that it's not actually time travel. They're just traveling to a parallel dimension that is 200 years behind. Thus, any changes to this timeline will not affect "their" present. Other episodes have the protagonist communicate with the future by placing ads in newspapers, something that wouldn't make sense if this was a parallel world.

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* Creator/JamesRolfe's film ''Legend of the Blue Hole'' speculates that the titular Blue Hole, a mysterious pond in the New Jersey pine barrens where people frequently vanish, is actually a time portal, and diving into it will cause you to resurface in the past. Jason and Samantha jump into the pond in 2003 and resurface in 1971, though Jason later draws a diagram showing that believes diving deeper into the Blue Hole would take you ever further back.

* In the short story "[[http://www.lexal.net/scifi/scifiction/classics/classics_archive/young2/young21.html Dandelion Girl]]", a person claiming to be a time traveler explains that time machines default to this mode, with their destination time advancing at the same rate as their source time unless you deliberately choose to keep resetting the destination back. Whether that person is telling the truth, however, is a rather important question...
* The {{Cool Gate}}s of the ''Literature/MorgaineCycle'' can do this as a side effect of their PortalNetwork function. Unfortunately, anyone who uses them to create a TimeParadox triggers a civilization destroying TimeCrash, which is why Morgaine is on her quest to destroy all the gates.
* The ''Literature/TimeScout'' series by Creator/RobertAsprin is based around an ever growing network of periodically opening portals, each of which is tied to a particular spot and reaches back a fixed length of time (which varies from portal to portal).
* Creator/MichaelCrichton's ''Literature/{{Timeline}}'' has a wormhole that was accidentally discovered during a teleportation experiment. The wormholes leads to the past, specifically, to France in 1357[[note]]Actually it's not the past - the novel makes a big point that it's not time travel, TheMovie on the other hand straight up calls it time travel. It's in fact a parallel universe who's time exists concurrent with ours, but is desynced so that its present is our 1357. Further, due to the quantum nature of universes, events in 1 are duplicated in all others. Hence a pair of glasses left in a universe where it's 1357 must also exist in the same place in a universe where it's 2001.[[/note]]. The events in the present and the past are synced, although it's also implied that YouAlreadyChangedThePast (i.e. no changes in the timeline are possible). When the quantum mirror is damaged by a grenade, the lead technician fears the connection may be lost for good, as they have no idea how the link works.

* In Creator/StephenKing's story ''Literature/TheLangoliers'', a "rip in time" causes all the passengers not asleep to disappear from a jet, while the plane and the sleeping passengers are sent back "a couple of minutes." The survivors must find out how to get back, and do so asleep, otherwise they too will disappear. They wind up a couple of minutes in the future but are able to sync up with normal time when it arrives.
* In ''Literature/ElevenTwentyTwoSixtyThree'', there is a stable portal in the back of a diner which leads to 1958. Interestingly, while time goes forward in the present, the other end always goes to the same second in 1958, effectively resetting on subsequent visits.
* Lynne Reid Banks' ''Literature/TheIndianInTheCupboard'' series has the magic of time travel function this way, with Omri's dad speculating that time is spiral in shape, and you can "drop through a certain number of layers" to get to a point in the past, but if you then take TheSlowPath (and live long enough) you eventually arrive back where you started. When someone is time-traveling using the magic, their present-day self is unconscious, so they have to be safely hidden and get back in time for nothing to go wrong (one side character is thought to have died as a toy-sized figure in what was, to her, the future because the people in her own time buried her seemingly dead body, and Omri's mother gets a nasty scare when she finds her husband and sons in the car looking like they somehow suffered carbon monoxide poisoning).
* The time doors in ''Literature/ChronoHustle'' can travel to multiple different times and places, but the time syncs up between all of them, so a day passing in one time equals a day passing in another.
* Creator/LesterDelRey's ''Literature/TunnelThroughTime'' involves the creation of a "time ring" that acts as a portal to the past.

* In ''[[Literature/MaryPoppins Mary Poppins Comes Back]]'', [[spoiler:after Jane accidentally cracks an antique Royal Doulton bowl, the boys in its design come to life, and invite Jane to see their home. After she enters the design, she winds up 60 years in the past. When the boys and their great-grandfather attempt to make Jane live with them forever, Mary Poppins intervenes, and rushes Jane back to her own time.]]
* ''Literature/TheBrotherhoodOfTheConch'': In ''The Mirror of Fire and Dreaming'', the titular MagicMirror serves as a portal from the present day to the Moghul Era.
* The [[MysticalCave smuggler's cave]] by the beach in Rex Stone's ''Dinosaur Cove'' series. Tom and Jamie use it during low tide to go back to prehistoric times by walking forward on the dinosaur tracks within, able to return by [[NowDoItAgainBackwards walking on the tracks backwards]] as long as the tide is still low, and their Wannanosaurus friend is usually not far from the other side.

* ''VideoGame/MarioAndLuigiPartnersInTime'' had time portals popping up all over the place, leading to different areas in the same time period.
* The Caverns of Time in ''VideoGame/WorldOfWarcraft'' are all about this. It would of course be difficult, incredibly confusing, and quite pointless to do it in any other fashion.
* The ''VideoGame/StarOcean'' series has a planet specifically dedicated to a PortalToThePast: planet [[WhatDoYouMeanItsNotSymbolic Styx]]. It's used about thirty minutes into ''VideoGame/StarOceanFirstDeparture'', mentioned in ''[[VideoGame/StarOceanTheSecondStory The Second Story]]'', and used in ''[[VideoGame/StarOceanTillTheEndOfTime Till the End of Time]]'' to [[spoiler: contact the 4th dimensional beings that observe our MMO universe. That's right! We're all game characters that got ''pissed'' and came ''out of the computer'' to tell our creators to ''knock it off''.]]

* The ''VideoGame/FinalFantasyXI'' expansion ''Wings of the Goddess'' introduced Cavernous Maws, intimidating-looking examples of this trope that connect present Vana'diel with the Crystal War era.
* In ''VideoGame/CityOfHeroes'', the Midnight Squad uses one to access the ancient Roman town of Cimerora. There is also a portal that allows players to visit the original versions of revamped zones, but no missions take place there.

* The door to the Timeless River within Disney Castle functions as this in ''VideoGame/KingdomHeartsII''.
* One of the main mechanics of ''VideoGame/Onimusha3DemonSiege'' is Time Dungeons. Locations where the 2 main characters explore simultaneously with 1 in the modern day and the other in the Feudal Japan era. The game's ExpositionFairy is able to use mirrors contained in those dungeons to traverse the 2 time zones, bringing essential information and tools with her. Though it does not seem that time continues to flow in her absence, at least while in those dungeons. Outside of those dungeons however time does indeed flow allowing the character she is not with to move through the world and arrive at the same location.
* A feature in one of the boss fights in the Dread Palace operation in ''VideoGame/StarWarsTheOldRepublic''. Players must enter both portals to the past and future to ensure that the boss is defeated in the present.

* ''VideoGame/Fallout2'' has a special encounter that's a ShoutOut to the original Star Trek, in which you find a time portal called the Guardian of Forever (both named and visually designed after the one from Star Trek) that takes you back to just before ''VideoGame/{{Fallout}}'', causing you to break the Water Chip and thus cause the events of the series.
* The hub world of ''VideoGame/CrashBandicoot3Warped'' is [[TimeMaster Dr. N. Tropy]]'s Time Twister Machine, and each level takes place during an era of history (or, in some cases, the future) that's accessed via a portal through its use.

* Sydney Scoville has caused a problem in ''Webcomic/GrrlPower'' by travelling back from a deployment through some sort of dimensional portal. She thinks she has been gone for a few days at most; her return point is 57 days into the future. This isn’t actually a plot point, as such, and isn’t a time travel story but it DOES cause a wrangle over what pay she is due.
* The eponymous energy sphere in ''Webcomic/{{Recursion}}'' is a portal to the past. [[spoiler:It also moves you through space as well as time: one end is on Celeria, while the other is in the distant past of Kass]].

* The ''WesternAnimation/{{Superfriends}}'' episode "The Time Trap" uses this trope.