Looks like Lulu's been "repairing" it again.
Clock tampering is the art of changing the time on a clock so that you could make time be in your favor and trick others into believing it to be the true time. Some kid may do this in school, when the teacher isn't looking, so he and his classmates can get out of school early, while an adult may make a clock go backward to forge his timecard and avoid getting in trouble with the boss for being late.
This trope is also used in mystery and thriller works, in which the murderer may alter the time on a clock to establish a false alibi about being somewhere else at the time of the murder.
Compare Clock Discrepancy.
- Detective Conan: When Ayumi stayed at her dentist's house, the dentist committed murder while Ayumi napped. The dentist altered the clocks and watched a recording with Ayumi she pretended was live TV, creating a witness for her false alibi.
- Tenchi Muyo!: In one of the manga issues, Ryoko pulls this prank on Sasami to make her think she's late for school. And all because Ryoko wanted to see the "Girl running late with a piece of toast in her mouth" trope for herself.
- The Grim Adventures of Billy & Mandy: In "Better Luck Next Time" (Cartoon Network Block Party #44), Billy is resetting all the clocks in the house for Daylight Saving Time. When he sets Grim's cursed cuckoo clock, he and Mandy gets sucked into a time vortex where a mysterious cloaked figure at the End of Time tries to return them before their presence causes a disaster.
- 101 Dalmatians: At the beginning, Pongo forwards the time on Roger's clock so he can go for his 5:00 walk in the park and get Roger and Anita, plus him and Perdita, to meet.
- In Die Feuerzangenbowle, this is part of a more elaborate, that is, downright epic school prank pulled off by the (alleged) student Johann Pfeiffer. While at his teacher Professor Crey's home, he sets back all clocks he can find by one hour, expecting "Schnauz" to believe his pocket watch is the one that's wrong, setting back that one, too, then his alarm-clock, and then being late for school the next day so that Pfeiffer can impersonate him. It ends up getting even better than this.
- Gremlins 2: The New Batch: In an attempt to trick the Gremlins into going to the lobby of Clamp Enterprises while it's still day, the protagonists blind the windows and set all the clocks in the building ahead a few hours.
- The Clocks: the murder victim is surrounded by six clocks, four of which have been stopped at 4:13. These clocks turn out to be Red Herrings. The unpublished book that the clocks imitated, however, directly implicated the killer as she was one of only a few people who had access to it.
- One Discworld book mentions that the clock tower of the Teachers' Guild strikes noon early, in accordance with all the teachers' wishes and prayers for class to be over.
- Nick Velvet: In "The Theft of Twenty-Nine Minutes", Nick is hired to ensure to ensure that the passengers on a riverboat cruise 'lose' 29 minutes. Getting a job as a Stage Magician on the riverboat's cabaret, Nick is able all of the clocks on the boat without being noticed. During his show, he collects the watches from all of the guests as part of a trick. As he places the watches in a bag, he uses sleight of hand to wind each one back 29 minutes. As they don't get their watches back till the end of the show, no one notices the change of time.
- In one of the St. Clare's books, Bobby Ellis sends their form teacher a summons to a teacher's meeting, and once the teacher leaves she puts the clock forward ten minutes. When the teacher gets back, confused and annoyed because no one else showed up at the meeting, she doesn't check the clock immediately - which leads to her ending class without giving the surprise test that she thinks the girls don't know about. While the class gets the test the next day, everyone has had a chance to study for it. Bobby would have gotten away with it completely if she hadn't tried a nearly identical trick as part of a practical joke just a few weeks later.
- The Thinking Machine: Crucial to how the murder was committed in "His Perfect Alibi". Once Van Dusen works out what the killer has done, he then has to work out how he did it.
- Columbo: Several episodes has the villain tamper with the clock in order to establish a false alibi.
- In "Fade in to Murder", the murderer uses this (combined with a video recorder) to establish an alibi. He slips up when he resets the watch of the friend he is using as an alibi: he sets it to right time, not realising his friend kept his watch five minutes fast.
- Death in Paradise: In "Beyond the Shining Sea - Part One", the killer secretly sets a witness's phone five minutes ahead: leading her to believe that she last saw the Victim of the Week alive five minutes later than she actually had. This throws out the supposed timeline of the murder, and allowed the killer to murder the victim and still establish their alibi.
- In the Doctor Who story "Ghost Light", the Doctor at one point puts the house's clock forward to 6pm because he's fed up waiting for the nocturnal characters to become active.
- Jonathan Creek: In one episode, the murderer fakes an alibi by adjusting the clock in his house in order to make a respectable Christian missionary (whom he is caring for while she recovers from an injury) believe that the current time was the time when the murder was committed when she saw him in the house.
- Note that in order for the murderer's plan to work, he needs to change the time a lot, by whole twelve hours — unlike most examples, this is a complex operation that happens over several days.
- M*A*S*H: The medics stage a patient emergency and turn the recovery ward clock back a half hour so Frank won't be able to operate a gun in bringing down 5 O'clock Charlie, an inept North Korean bomber.
- Mr. Bean: In "Happy New Year, Mr. Bean," he invites his neighbors for an impromptu New Year's Eve party. Snacks include twigs dipped in Marmite (!) and sugared vinegar (!!). They immediately turn his clock to midnight, "ring in" the new year, and head to a real New Year's party. He wakes up to the sound of a party at what he thinks is 3:00 AM, and realizes that they've tricked him big-time.
- NewsRadio: One episode has Jimmy in a deal to sell the station with a midnight deadline. While the staff tries to convince him not to do so, Matthew reveals that he set the clock back and the midnight deadline had actually passed. Jimmy tells him that the deadline was just a guideline and they still have time.
- Seinfeld: Inverted in "The Susie"; Kramer decides to ignore Daylight Savings Time one year, only to repeatedly find things happening one hour late.
- Veronica Mars: A third-season episode has a social science class run an experiment. One group of students will represent members of a terrorist group who have been arrested while another group represents the prison guards. The inmates' goal is to avoid revealing the location of a bomb before a certain time while the guards' goal is to get them to reveal it. In the end, the "guards" trick the "inmates" into giving up the location by setting the clock ahead and making them think they've succeeded.
- The central mechanic behind Fun House seems to involve changing the amusement park's clock to midnight, thereby making Rudy the ventriloquist dummy go to sleep and granting the player full access to the fun house.
- Deponia Doomsday: To get out of holding a lecture Rufus fast-forwards time in the building using a spacetime anomaly.
- Danganronpa 2: Goodbye Despair: This is done in the 4th case by Gundham Tanaka to initiate their murder plot. While all the students were trapped in the funhouse, they are required to attend Monokuma's Tai-Chi lessons in the tower at 7:30 AM sharp, else they be punished. Gundham sets all the clocks in the funhouse back 2 hours while everyone was sleeping, making everyone believe that they still had more time to sleep (they were close to starvation and dehydration, so they wouldn't try to exert themselves). Because of this, the only one to go to the tower was the robotic "Mechamaru" who had a built-in clock tuned to the proper time. There, Gundham intercepted him alone and enacted his murder.
- Vermillion Watch: Order Zero: The zoo you need to search has a time-controlled automatic gate. To get in, you need to reset the clock controlling it.
- Arthur: In the prologue to "The Last of Mary Moo Cow", Arthur sets every clock in his house to 4:00 to trick D.W. so he can watch Dark Bunny. It doesn't work, since D.W. doesn't know how to tell time.
- DuckTales (1987): In "Allowance Day", Huey, Dewey and Louie trick Uncle Scrooge into thinking it's a day later than it is so they can get their allowance before a sale on a scooter ends. The problem is, Scrooge is so influential and well-respected that all his business partners assume it is the next day, and their error travels to people all across the globe. This includes the shopkeep, so the triplets still miss their sale, and the general of a Banana Republic, who says Scrooge missed his shipment date.
- Family Guy: In "Stuck Together, Torn Apart", Peter and Lois have a trial separation, and Quagmire leaps at the chance to ask Lois out. As she says she needs some time to think it over, Quagmire smashes open a wall clock, turns the time forward, and asks "How about now?"
- G.I. Joe: A Real American Hero: A bomb is planted in a building, and the only one who knows where is a COBRA agent being interrogated in the same building. Shipwreck sets the clock faster so, when the agent inevitably admits bomb's location to save himself, he'll have more time to defuse it.
- The Goofy short Teachers Are People has a student doing this to make school end early, just as the narrator says "Little hands make the time pass quickly."
- Hi Hi Puffy AmiYumi: The episode "Time Off" has Yumi setting Ami's alarm clock ahead a few seconds to get a few more moments of sleep. However, because Ami is such a Schedule Fanatic, she ends up doing things a few seconds later than normal.
- Little Lulu: Besides the trope's mention in her theme song, the short Lulu at the Zoo has Lulu fast-forwarding a clock to she won't have to wait for a 2:00 tour of the zoo.
- Looney Tunes
- In "Swooner Crooner", several chickens punch the clock at Porky Pig's egg plant; one chicken arrives late and sets the clock back before punching in.
- In the first Ralph Wolf and Sam Sheepdog cartoon, Don't Give Up the Sheep, Ralph changes Sam's punch clock to trick him into thinking that it's quitting time so that he leaves, giving him a free shot at the sheep. Sam is just leaving when he sees the time on a clock tower and runs back just in time to stop Ralph.
- In "Tweet Tweet Tweety," Sylvester changes the clock to a few minutes early so he can jump into the Old Faithful geyser to try and snatch Tweety. Tweety has already escaped the crater and goes on to move the clock to 12:00. Old Faithful erupts on the spot, taking Sylvester up and down with it.
- "Porky's Badtime Story" has Porky Pig and Gabby Goat arriving at work late. Gabby turns the punch clock back two hours and tries to clock in—the clock makes some ungodly noises that brings their boss over. (Remade as "Tick Tock Tuckered" with Daffy Duck in Gabby's place.)
- Recess: In "The Spy That Came in From the Playground", T.J. and the gang show their new friend James around their operation by setting the clock forward to get out of school early. The next day, they find the clock caged off to prevent them from doing it again (thanks to James actually being an adult mole sent by the district to shut down the T.J. operation from the inside).
- Regular Show: In "Saving Time", Benson orders Mordecai and Rigby to set the park clocks back for Daylight Savings Time, but they decide to prank him by setting the clocks to the wrong time (along with the clocks on Benson's apartment). This causes the park and Benson's apartment to move to the correct time zone, right in the middle of the ocean!
- The Simpsons: In "The Boy Who Knew Too Much", Mrs. Krabappel announce the discovery that the clocks have been running early for a long time, so class that day is being extended by two hours. Bart groans and begrudgingly looks at the Lil' Bastard Clock Tampering Kit hidden in his desk.
- TaleSpin: In "The Time Bandit", a Recycled Script from the DuckTales example above, Baloo alters the clocks and calendars (and even bribes a radio show host to say the incorrect day) to trick Rebecca into thinking it's Saturday and pay him so he can attend a party at Louie's. This causes a chain of events that end with Rebecca nearly getting executed in Thembria.
- Some schools have their clocks bolted shut or caged off to prevent such incidents from happening. Others have the clocks mechanically linked to each other so they will be in sync and can only be altered from a secure office.
- This is a common trick among gamers to manipulate their gaming system's clock in order to trick a game into thinking a lot of time has passed, e.g. to solve a real-time Waiting Puzzle or to take constant advantage of events that only happen every x hours/days, although most games that have this as a major part of their gameplay have some kind of mechanism to prevent it, such as ignoring the system clock and using server time instead or checking that the current system time isn't in the past when compared to the latest save game timestamp.