Time loop

A time loop is a fictional situation in which time runs normally for a set period (usually a day or a few hours) but then skips back like a broken record. When the time loop "resets", the memories of most characters are reset (i.e. they forget all that happened). This situation resembles the mythological punishment of Sisyphus, condemned to repeatedly push a stone uphill only to have it roll back down once he reached the top, and Prometheus, condemned to have his liver torn out and eaten by an eagle each morning. The plot is advanced, however, by having one or more central characters retain their memory or become aware of the loop through déjà vu.

The best-known example of this is in the 1993 film Groundhog Day, although time loops had appeared in many fictional works prior to that. Stories with time loops commonly center on correcting past mistakes or on getting a character to recognize some key truth; escape from the loop may then follow (this can be seen as a metaphor for reincarnation).

Time loops are a common plot device in science fiction, especially in universes where time travel is commonplace.

References

Television

The following series featured time loops as a main theme or at least fairly frequently:

Code Lyoko - Time is reset at the end of each episode in the first season, but seldom in the second and third; called a "return to the past" or "return trip".
Day Break - A police officer relives the same day over and over, and has to figure out how to save himself and those close to him from a host of threats.
Several episodes of The Dead Zone have a virtual time loop by virtue of Johnny Smith living out several versions of the same future scenario through his psychic foresight.
Doctor Who is all about time travel. A number of episodes involve or make mention of time loops: "Image of the Fendahl", "The Invasion of Time", "The Armageddon Factor", "The Claws of Axos" and "Meglos" (referred to as a chronic hysteresis). The Master's use of the term "time loop" in "The Claws of Axos" may be the first instance of its use to describe the phenomenon. Beyond the original TV series, the term also appears in the radio play "No More Lies", starring the eighth doctor, Paul McGann.
Seven Days - Alien technology allows one person to go back in time seven days to prevent whatever catastrophe is typically shown in the show opening.
Card Captors - The Time card manipulates time meaning Sakura and Syaoran Li must repeat the same day over and over again until the card is sealed. Both of the characters keep their memories while everyone else loses theirs at the end of the daily cycle; both characters use this situation to their advantage.
Tru Calling - A woman named Tru Davies works at a morgue, where dead bodies make requests for help. This sends her back to the beginning of the day so that she can attempt to save the person's life.
Higurashi - The story is shown as chapters with variations of what happens. Usually the chapters end with the death of the main characters but the next chapter begins the story again with them alive.

Time loops have been featured in individual episodes of many TV series, including:

TV Show	Episode	Comments
Andromeda	"When Goes Around..."	It's also hinted that Trance Gemini has experienced the show's time-line several times.
Angel	"Time Bomb"
The Angry Beavers	"Same Time Last Week"
Buffy the Vampire Slayer	"Life Serial"
Charmed	"Deja Vu All Over Again" "The Good, the Bad, and the Cursed" "Show Ghouls"
Crime Traveller	"Final Episode"
Early Edition	"Run, Gary, Run"
Fairly Oddparents	"Christmas Every Day!"
Farscape	"Back and Back and Back to the Future"
First Wave	"Gulag"
Justice League Unlimited	"The Once and Future Thing: Time Warped"
Lois and Clark	"'Twas the Night Before Mxymas"
Medium	"Be Kind, Rewind"
Monty Python's Flying Circus	'Déjà vu' (skit, a.k.a. "It's the Mind"), episode 16.
The Outer Limits	"Deja Vu"
Pepper Ann	"'T.G.I.F"
"Power Rangers: Lightspeed Rescue"	"Yesterday Again"
Totally Spies!	"Deja Cruise"
Red Dwarf	"White Hole"
Red vs. Blue	"Have We Met?", "Same Old, Same Old"
Smallville	"Reckoning"
South Park	"Cancelled"
Stargate SG-1	"Window of Opportunity"	The episodes "The Gamekeeper" and "Avatar" also feature time repeatedly "reseting" itself, but they both take place virtual reality universes, whereas "Window of Opportunity" takes place in the real world and is the only instance of the term "time loop" being used in the series.
Star Trek: Enterprise	"Future Tense"
Star Trek: The Next Generation	"Cause and Effect" "Time Squared"
Star Trek: Voyager	"Coda"
The Twilight Zone	"Shadow Play"
Weird Science	"Universal Remote"
The X-Files	"Monday"
Xena: Warrior Princess	"Been there, Done that"

Music video

“7 Days" [1] (2000) from Born To Do It by Craig David.
"Ocean Avenue" (2004) from Ocean Avenue by Yellowcard.
"Grounded" (2001) from Finelines by My Vitriol.

Film

12 Days of Christmas Eve - a mix of time loop and "A Christmas Carol". A cold-hearted executive is given the chance to replay a Christmas Eve twelve times, with a horrible fate in store if he does not change things for the better by the twelfth replay.
12:01 PM and 12:01 - two films (a 1990 short and a 1993 full-length), based upon Richard A. Lupoff's short story of the same name.
Christmas Do-Over - a bitter divorced man finds himself reliving the same Christmas Day and trying to use it to reconcile with his ex-wife and son.
Christmas Every Day - A 13-year-old boy relives Christmas day again and again.
The Glitch - (short, directed by Mike Samonek, staring Jason Biggs) - A guy on a date gets caught in a loop.
Groundhog Day
The Last Day of Summer
Mickey's Once Upon a Christmas - retells Christmas Every Day with Huey, Dewey and Louie.
Nirvana - time loop happens to a fictional person in a virtual reality game.
Primer - Film deals with a time loop that is described as being like a cul-de-sac with an "A end" and a "B end".
Retroactive - A psychiatrist returns repeatedly to the same point in time to prevent a murder.
Run Lola Run - not quite a time loop, but three versions of the same twenty minutes in Lola's life, if she makes different decisions.
The Lake House - this film has time-loop like features: Two characters exist in different time frames, and affect each other's lives. The ending of the film is a causality paradox, which if followed through would cause the timeloop to repeat.
Taan ("Turn" in English) - Japanese romance film; a character continually relives one day.
Zerkalo dlya Geroya( Mirror for a hero)- Russian perestroika-time film where the guy from 1987 falls 40 years back in time to Stalin era and lives there the same day over and over

Literature

"12:01 PM", a 1973 short story by Richard A. Lupoff.
Dark Tower, a Stephen King series featuring many elements of time travel, including a time loop.
"Escapement", a 1956 short story by J. G. Ballard.
"HELP! I'm Trapped In the First Day of School!" by Todd Strasser. A boy keeps repeating his first day of school. A later book in the series features the same character being trapped in the first day of summer camp.
I Am the Cheese. Technically not a true time loop novel, but the young main character, who is revealed to be insane, acts out the same week over and over.
"A Little Something For Us Tempunauts", a 1975 short story by Philip K. Dick.
The Neverending Story, a book by Michael Ende - a time loop is deliberately set in motion at one point to force Bastian's hand.
The Plot To Save Socrates, a novel by Paul Levinson.
Tales from the Time Loop, a book by author David Icke.
Replay, a Ken Grimwood novel in which the main character suddenly shifts to much earlier in his life, then relives shorter and shorter periods.
"That Feeling, You Can Only Say What It Is in French", short story by Stephen King.
Several stories from the Ijon Tichy series by Stanislaw Lem.
Time Trap and Back To The Time Trap by Keith Laumer.
The Details of Nikita Vorontsov's Life by Arkady Strugatsky.
In the fifth novel of the Haruhi Suzumiya (light novels), there is a chapter called Endless Eight where Haruhi Suzumiya creates a time loop that Kyon eventually breaks.

Video games

Astro Boy: Omega Factor - The first time Astro experiences the game's story, at the end of the seventh stage, his story ends in a scene where all robots are destroyed by the mysterious entity known as Death Mask. After the end credits are shown, Astro is given another chance to experience the same events, and must solve the mystery behind the Death Mask in order to access the game's true final level and ending.
Breakdown - In one section of the game the main character experiences an illusion that causes him to repeat the last few seconds of what just happened.
Chrono Trigger and Chrono Cross both deal with the concept of time, with the older Chrono Trigger focusing more on different time periods in the same timeline and the younger Chrono Cross dealing with alternate realities.
Dragon Warrior VII - One town in this game is placed under a curse so that the same day is repeated, with only the heroes, not native to the town being cursed, knowing that there is a time loop.
Ephemeral Fantasia - The game centers around a five-day time loop, about which only the hero is aware.
Fate/hollow ataraxia - The main characters Shiro and Bazett are trapped in a four-day time loop.
Final Fantasy - Garland, once loyal knight of the Kingdom Coneria(Cornelia), is sent back 2000 years into the past. There he became Chaos, the Master of Evil, and sent the Four Fiends of the Elements ahead 2000 years into the future, where they would send him back in time. Garland/Chaos theorized that in 2000 years the time loop would close and he would cease to exist, which he thought would make him immortal.
Final Fantasy VIII - The first sorceress you fight in the game, Edea, is actually possessed when the player fights her, and after losing her powers, she eventually tells Squall, the protagonist, about how she gained her powers. She gained her powers by accepting them from a fallen sorceress, in order to protect the children at the orphanage from coming in contact with the sorceress. At the end of the game, it is revealed that a sorceress from the future was sent into the past after being defeated by Squall. This happens due to "Time Compression", which resulted in past, present, and future being combined. The sorceress then passes her powers on to Edea, enabling her to posses Edea before her death.
GrimGrimoire - The main character is stuck in a time loop and has 5 days to try to stop a disaster.
Higurashi no Naku Koro Ni - Each chapter is a different iteration of the same month, with only one character being aware that she is living in a time loop.
The Legend of Zelda: Majora's Mask - The entire game is set around a three-day time loop, which the player can reset at any time they please.
Prince of Persia: The Sands of Time - The player is given the "Dagger of Time," allowing them to continuously relive the previous ten seconds of game-play for a set amount of times, or until the player is satisfied with the way he or she played those ten seconds.
Shadow of Memories aka Shadow of Destiny - The game begins with the death of the player, which the player then needs to prevent.
TimeSplitters: Future Perfect - The antagonist, Crow, goes around time, and the protagonist, Cortez runs into him. At one point the older version of Crowe gives all of his research to the younger version of himself, and they both leave to continue this. There are also several loops in the game, as you are helped out by a future version of Cortez, and then you eventually play the part and help the past version of a Cortez.
Escape from Monkey Island (2000) - In one portion of the game, the player has to repeat the actions of the second Guybrush encountered earlier. If not performed identically (because at this point in time, the player is now the earlier second Guybrush), the player is returned to the start of the swamp.
Sonic The Hedgehog (2006) - the Blue Chaos Emerald is a bit of a paradox as it is used by Shadow the Hedgehog. He gave it to Silver The Hedgehog who gave it to Elise and it ended up with Sonic the Hedgehog, but the game must have been before the events of Shadow the Hedgehog (video game).