At the end of Ayashi No Ceres, it's revealed that Tooya has only a year or two left to live. Both Tooya and Aya know it, hence the scene where Tooya begs Yuuhi to take care of Aya and their baby when he kicks the bucket.
Bokurano. The cast soon learn that this is true for the whole lot of them as Zearth's pilots; a lottery picks out who'll be next, and the time is decided randomly. The main story is arguably to see how each of the characters deal with this knowledge, in light of their own lives.
In Busou Renkin, when Kazuki becomes a victor he has six weeks before the change becomes permanent. He vows to kill himself before his Superpowered Evil Side becomes permanent.
In Chrono Crusade, Rosette made a contract with Chrono, a demon, saying that she will give him the ability to use his powers at the cost of her own lifespan. The sign of their contract is a watch Rosette wears around her neck, which literally counts down the time she has left to the very minute.
Also, it's revealed in flashbacks that Mary Magdalene had seen visions from her childhood that she would be killed by someone named Chrono. Once she meets him, she's well aware that it means she will soon die by his hand, but willingly leaves with him anyway, believing that You Can't Fight Fate.
The only power of Oruha in Clover is to know the exact moment she will die. And the readers know too, if they started reading the volumes in order.
In recent chapters of the newly revived manga D.N.Angel, Satoshi has told Daisuke that all members of the Hikari family die young, and he believes he's near his own death.
In Fate/stay night : The servants. Their reason to materialize in the human plane is solely to participate in the Holy Grail Wars; after that, they effectively 'die'. By a matter of fact, they are summoned specifically to die, their energy of an heroic-spirit is needed to fuel the Holy Grail.
This trope is applied best in the route Fate.
Due to the incredible strain of keeping the family in some sort of order, the heads of the Sohma family in Fruits Basket never live past thirty. That's what, in fact, made Akito's father Akira an Ill Boy... and ultimately killed him. Akito shows signs of illness in the anime and that's her Freudian Excuse, but in the manga her bad health seems to come more from deep seated psychological problems, courtesy of her Manipulative Bitchmother; when she gets better, the signs of illness seem to disappear.
In G Gundam, the siblings from Neo Mexico Gina and Chico Rodriguez already know that Ill Girl Gina's Soap Opera Disease is incurable and that she's almost done with her life. Chico becomes the Neo-Mexican fighter not to get a miracle cure, but to bring her to Earth and give her a chance to die peacefully. Thanks to Domon and Rain, they get it.
Grave of the Fireflies has a scene in which Seita and Setsuko, the brother and sister who serve as protagonists, capture a large number of fireflies and keep them nearby overnight. The next morning, all the fireflies are dead. Given the number of people who are killed by bombs or starvation in the movie, as well as its connection to the title, this scene is obviously meant to represent something beyond dead insects.
Motorball champion Jashugan in Gunnm. The modifications that make him the elite athlete/fighter that he is are killing him, but he'd rather go down defending his title than retiring.
In Inuyasha, Miroku's Wind Tunnel is a curse inherited from his father which dooms him to an early death unless the source of the original curse, Naraku, is killed. After an incident in which he absorbs massive amounts of toxic miasma trying to take Naraku out so that Kohaku won't have to be sacrificed, the time frame of Miroku's impending death moves up from "sometime in the nebulous future" to "any day now." When Naraku is defeated, said Wind Tunnel disappears.
In Kanon, the foxes on the hill overlooking the town can use a miracle to become human, but they must give up their memories and their life to do so, meaning they won't live very long after their miracle occurs, so they have to live their remaining life to the fullest while they can. This explains the while deal with Makoto Sawatari... she is one of these foxes..
The conceit of Mahoromatic, where the protagonist is a gynoid with limited battery life remaining. Each segment of the anime and manga ends with how many days she has left to live.
This gets parodied in Disgaea 3 with the hours it's left before Almaz becomes a demon. No such thing ever happens.
The 'players' in Mirai Nikki have what is known as a BAD END: When their future-revealing diaries get an entry that reveals when they'll die, death is all but certain to occur at that point. There is a chance to Screw Destiny involved and the main character has managed to do this several times, in no small part due to his Stalker with a Crush's device, which gives fine-detail information about the how as regards to him.
Also, it turns out that the reason for the game is that the god of that world's days are numbered, and the world will end if that happens before he finds a successor. Why that issue needs to be solved with a no holds barred Battle Royale is anyone's guess, but God Is Evil in this series.
Of noteworthy mention (and for reasons unrelated to her health) is Yuno. Her days are numbered because she essentially volunteers to die at the game's end so that Yuki can become a god.
Yoite in Nabari no Ou uses a dangerous jutsu called Kira which essentially kills his targets using his own life force as bullets. As a result, he's dying by inches throughout the series, since every time he uses his power he loses a bit of his life that he can't get back. This is a source of non-stop anguish.
Xerxes Break in Pandora Hearts. His body is slowly breaking down from the strain of being Mad Hatter's contractor. Mostly because it's the second time he's been a contractor. The first time was an illegal contract.
Ashitaka spends most of Princess Mononoke with a curse on his arm that is slowly spreading until it will kill him. When the Forest Spirit gets its head back, Ashitaka, San and the villagers with leprosy are cured.
The Reveal of Puella Magi Madoka Magica, magical girls realizing the fact that an overused and darken Soul Gem caused from depression and sadness will turn themselves into the very monsters tribe they're hunting. No Puella Magi can escape this fate, and there's no way to change the rule, well, except one.
A later revealed part of the back story of Gold Roger of One Piece is that he had contracted an incurable terminal illness that gave him a limited time remaining to live. Being a Bad Ass, he decided that, if he was going to die anyway, he might as well conquer the Grand Line first. He does, making him the only person thus far to manage it. It's also the reason the Marines were able to capture and subsequently execute him, as Roger turned himself in as part of a Thanatos Gambit.
A huge part of Coach Munakata's character and motivations in Aim for the Ace! are centered on how he has three years to live due to leukhemia.
Alfons Heiderich from the Fullmetal Alchemist movie, Conqueror of Shamballa. He knows he's gonna die soon of cancer due to breathing rocket fumes, and he's desperate to finish his project for the rocket in time.
The premise of Ikigami: The Ultimate Limit is that anytime at all, anyone between the age of 18 and 24 might get their "death papers", informing them that they have 24 hours left to live.
This is the basis for All-Star Superman. With only a year to live due to solar radiation poisoning, Superman decides to get his last few odds and ends in order, finish off those last few bad guys, finally open up fully to Lois and maybe give Lex Luthor one last thrashing.
This is part of the plot of Young Liars. In the first chapter, the reader learns that Sadie, one of the main characters, survives a gunshot wound to the head, but is told by the doctor that sooner or later, she will die due to the bullet slowly migrating through the skull.
Slightly subverted in Transmetropolitan. Spider Jerusalem learns that his mind is decaying as a result of a buildup of a certain dangerous nanotechnology in his brain—the effects are similar to Alzheimer's Disease. He is given an amount of time before he degenerates to a state of helplessness, but instead of wallowing in misery or angst, he takes a moment to feel the fear and grief, then he collects himself and tells his assistants that... well:
Channon: Spider... what're you going to do? You might not be able to write a year from now. Or anything.
Spider: *magnificent bastard grin* So we've got a deadline. We can do deadlines.
And in a final subversion he turns out to be part of the one percent of victims to recover, though he keeps this a secret.
This is the fundamental concept of Strikeforce: Morituri, where the heroes gain super-powers (to fight off an Alien Invasion) via a process that kills them inside of a year. Notably highlighted when they are reprimanded for attacking the aliens without authorization; in response, Ruth "Toxyn" Mastorakis administers a poison to her teammates, then explains it as the desperation the Morituri feel every moment they are kept away from active duty.
Once perpetrated on X Man - essentially, there was something in his genes that would lead to his death in the near-future. Warren Ellis, who wrote subsequent issues of the comic, referred to it as the "Dead At 21 TV Plot Engine" and advocated getting rid of it as fast as possible.
The Batman Dailies once featured a story about a man with 10 days left to live. Oh and he was getting married when he found out about it.
The surprisingly good 1 Month 2 Live. A Marvel Comics story set during the Heroic Age company-wide event. An ordinary man is exposed to toxic chemicals a la Daredevil. While he does gain powers, he also gains terminal cancer and the prognosis in the title. The book then becomes the story of the man and his family desperately trying to find a cure.
The replicants in Blade Runner have returned to Earth to find away to extend their four-year lifespan, but it is in vain.
The end of the second Death Note movie, and the L spinoff movie, relies on this. L managed to write his own name in the Death Note, which gives him exactly 23 days of life. He uses them to keep investigating and working.
Connor and Heather in Highlander, and all immortal/mortal love stories since, as the character says: "You are all dying. Twenty years, six months, what's the difference?"
The main character of Joe Versus the Volcano is told by the doctor that he's got X days to live, and then some rich guy offers to let him live the rest of his life (what little there is) in luxury, if he will, in return, jump into a volcano and thus mollify some volcano-god-type who's been getting in the way of his Tropical Island mining project. This is actually a subversion, since in the end it turns out that the doctor had been bribed by the rich guy, and had lied to Joe so that the guy could get the human sacrifice he needed.
In the fantasy movie Krull, the cyclopes were beings with two eyes, but they bartered away their second eye to The Beast in order to see the future. The Beast instead tricked them, and the only future they can see is the time of their own death.
This trope is the premise (and sometimes the whole plot) of many romance movies - examples include Autumn in New York, Sweet November, etc... and, of course, the eponymous Love Story.
This trope is often the premise of certain dramas where the main character either has to accomplish some particular thing or set of things before they die (usually this requires not letting other people know that they're going to die), as in Ikiru or My Life Without Me.
Anyone who sees the cursed video tape from The Ring is slated to die in seven days.
The Shootist is about an ageing gunfighter (played by John Wayne) who discovers he's dying of cancer at the dawn of the 20th century and has only weeks to live. Eerily, after making the film Wayne was diagnosed with stomach cancer and died, making The Shootist his last picture.
The entire premise of Logan's Run, a dystopian future Sci-Fi in which the population issue is addressed by mandating that everyone dies on reaching the age of 30.
In Never Say DieBob Hope's character was misdiagnosed with a terminal illness and decided to marry Martha Raye's character in order to avoid being the target of a wealthy "serial widow" who intended to become even wealthier. Fortunately, by the time he realized he wasn't dying after all they'd come to care for each other.
The Trope Namer is The Book of Daniel, in a sequence that gives us three common phrases. "The Writing On The Wall" appears to a Babylonian king, specifically the words MENE MENE TEKEL UPHARSIN. This is simply a list of weights and measures, but is translated as a metaphor: "You have been weighed in the balance and found wanting, Your Days Are Numbered, and your kingdom shall be divided by the Medes and the Persians".
The Bible also makes mention of how short and insignificant human life is in comparison to the rest of the universe. Your measly life of 80 odd years, maybe a hundred if you are lucky? It is likened onto a vapor or smoke, one moment it is there and the next it is gone as it is swept away by the wind. God who has existed since the beginning of the creation of the universe sees all of your lives, all of your struggles and all of your triumphs as if they were blinks of his all-seeing eyes, they end in mere moments. The message is clear, it is humbling that an immortal, all-powerful, all-knowing God cares enough about you that he intervenes in our lives and how important it is that we take advantage of the days that are given to us.
It takes Gilgamesh a long time to accept that he has to die, but once he does, life somehow gets better for him.
Elizabeth aka Beth realizes her days are numbered in Little Women Part Second and spends her last year in a room that her family have turned into a little corner of paradise for her before the inevitable Tear Jerker death scene.
Played with in Harry Potter with Dumbledore, though you don't find out until the next book.
Also with Harry himself.
Subverted in the Discworld series, where the anthropomorphic personification of Death has an hourglass for every living being on the Disc, counting down accurately to their death... except the wizard Rincewind, whose personal timeline is so messed up at this point that not even Death knows when he'll die.
Wizards and Witches also have pre-emptive knowledge of when they're going to die, and thus tend to use this knowledge to put their affairs in order. Witches use it to make sure a replacement is found, bequeathing her personal items, making sure a grave is dug, and so on, while Wizards tend to commit credit fraud and drink themselves into a stupor. Both sides like to throw a good last party with their friends/colleagues as well.
Of course, the lifetimers are physical objects, and rather fragile at that. Several are destroyed and/or fall to the ground and smash during the course of Death's fight with Mort, which makes the nearest convenient death occur instantly (although one man who almost dies of falling is caught on a tree branch because one of the other characters catches his lifetimer).
Also, at least one being on the Disc can ignore lifetimers at will - Death himself. In addition to the old trick of simply not collecting the dead in question, at one point Death turns over Mort's lifetimer, giving him extra time.
But Death is specifically not supposed to do that, leading to a Crowning Moment of Heartwarming in Hogfather, when it's time for The Little Match Girl to die in a cold, dark alley, and Death is having to spend the night pretending to be the Hogfather.
Albert: You ain't really allowed to do that.
Death: The Hogfather can. The Hogfather gives presents. There's no better present than a future.
Even Death has a lifetimer - it's huge, ornate, and completely empty. Read into this what you will.
In all fairness, to extend the metaphor, it's in fairly large print.
There are a few other beings in the Discworld not subject to death. Basically, any Anthropomorphic Personification (and sometimes heirs to such) is a peer of Death. Also, anything anything above him, like the Auditors, plays by a different set of rules.
Taken literally in Animorphs when the last of the Arn, who are extremely adept in biology, is capable of pinpointing to the exact day how long he expects himself to live. As the Animorphs don't trust the Arn, Ax gives the subtle threat that "biology isn't the only factor".
In "The Cold Equations" by Tom Godwin, an 18-year-old girl sneaks onto a space shuttle on a lark. But the ship doesn't have enough fuel to land with her on board. She can go out the airlock involuntarily, or voluntarily, or the ship will crash. The universe doesn't care which. Published in 1954, the story subverted the usual notion in Golden Age science fiction that all problems could solved through the power of Science.
Terry Brooks played with this trope in The Wishsong of Shannara. Bremen informs Allanon that if he continues with the quest the heroes are on, he will not live to see its end. Bremen also informs him what it will be that kills him and why it must happen. Allanon isn't thrilled with this news and, briefly, does try to avoid a confrontation with his future killer. When he accepts his death is inevitable and absolutely necessary, he chooses to Face Death with Dignity thus ensuring that the Cycle of Magic can come to a close once the quest is completed.
Whomever watches the cursed videotape in The Ring (the original book as well as the movies) will die in seven days unless they figure out how to break the curse. Likewise Samara/Sadako probably figured that being stuck at the bottom of a well boded ill for her chances of survival.
Orlando Gardiner in Otherland is a teenage boy with progeria, a genetic disease that causes rapid aging and is invariably fatal. He lives his life mainly online, playing a virtual hero while his real body wastes away.
In Death With Interruptions by Josť Saramago, Death starts sending purple envelopes to people that arrive one week before their death, to give them some advance notice.
In The Mortal Instruments, when Clary destroys Valentine's ship with a single mark, an awed Valentine says "Mene mene tekel upharsin", in reference to the Biblical quote above. It's given an Ironic Echo later when Clary engineers the failure of all his plans as well as his own death. He's sealed her mouth, so she writes "MENE MENE TEKEL UPHARSIN" in the sand at his feet.
The main character in Jack Ritchie's "For All the Rude People" was diagnosed with a terminal illness which gave him two or three months to live, if he was lucky. He decided to spend his remaining time disposing of everyone who'd ever been unreasonably rude to another person, starting with the candy store owner who'd snapped at him for spending "all day" deciding what to buy with his "lousy nickel" when he was a child.
Live Action TV
The main premise of the obscure MTV series Dead At 21, in which the fugitive victim of a government experiment has one year to keep intelligence-boosting microchips from burning out his brain.
In the Heroes episode "Seven Minutes to Midnight", a waitress named Charlie is murdered in the diner in which she worked. In a later episode in that season, "Six Months Ago", Hiro travels back in time to prevent Charlie's death, only to find out that she has a blood clot in her brain that will kill her soon, no matter what.
And then, in a surprising twist in the FAR later "Once Upon a Time in Texas", Hiro returns to the past again, crosses his own timeline, and saves her and removes the clot in a particularly risky trade by effectively telling still morally-confused Sylarthat he is destined to be a villain. Hiro ends up telling him that by the time he's come back, Sylar had already died alone. He managed to prevent Charlie's doom and (unknowingly mis)inform Sylar of his own.
Dean on Supernaturalsold his soul to a demon in exchange for Sam returning to life and was given only one year until the contract came up and he died.
In the NCIS episode "Dead Man Walking," Ziva becomes very close to Lt. Roy Sanders while he is dying of radiation poisoning, causing her and Jenny considerable distress.
Charlie and Locke from LOST both get in this situation, albeit differently. Charlie nearly all of Season 3 with the knowledge that he's doomed due to Desmond's prophetic visions, while John Locke is explicitly told by Richard that he's going to have to die (which we already knew he was dead, as of the end of season 4, which is one of the mysteries of season 5. Locke is resurrected. Except he isn't.
A minor character in season seven of Buffy the Vampire Slayer had future-seeing powers and knew exactly when she was going to die (a few days from when she was introduced, at age 16). A whole episode revolved around Buffy and the gang trying to protect her while convincing her that she might live. They were wrong.
Buffy herself had the prophecy in the Season One finale. She died, but it didn't stick.
From FlashForward (2009), Demetri didn't have a flash forward, making him fear that he won't live up until those six months.
The Doctor's tenth incarnation got a lot more warning about his impending death than the previous ones, thanks to the "knock four times" prophecy.
The Fourth also got a preview in the form of The Watcher.
On the other side of this trope, the Sixth Doctor spends about an episode of "The Two Doctors" taking unnecessary risks and generally moping about when he believes he is about to be erased from existence due to a time paradox of some sort.
Eleven was told this in the 2011 series, with the added complication of his companions watching his future self being killed. He got out of it, naturally, but decided to let much of the universe think he hadn't, as his Memetic Badass reputation was becoming more of a hindrance than help.
The Orphenochs in Kamen Rider Faiz are doomed to short lives, including The Hero Takumi. At the end of the show he has surgery in the hope of prolonging his lifespan, but it is implied that he will not survive long. Kaidou, the only other surviving Orphenoch on the heroes' side, has not had the procedure and is also doomed.
Akira Date in Kamen Rider OOO has limited time to live due to a bullet lodged in his brain, although he eventually recovers after leaving to have surgery.
Used in Highlander, when the immortal Methos falls in love with terminally ill Alexa Bond and tries to cure her by finding the Methuselah stone.
The plot of both series of Garo. In series one, Kaoru is covered in the blood of a Horror, and will die within 100 days. In series two, all Makai Knights in the show are branded with a cursed seal that is slowly killing them.
In Season 4 of Fringe, September, an Observer, appears from the future when he gets shot by Jessica he tells Olivia that, "in every possible outcome you have to die" when she is waiting for Lincoln and Peter to return from the other side. In the season finale she is shot and killed by Walter to prevent the collapse of both Universes, however, she is resurrected by the Cortexiphan in her system (debatable fulfillment of September's prophecy).
Early in the second season of 24, George Mason is exposed to a lethal dose of radiation and is told he has a day or so to live. Twelve episodes/hours later, he takes Jack's place in making a Heroic Sacrifice.
The plot gets reused in season seven when Jack is infected by the terrorists' weapon and will die within hours, which means he has to bring the villains to justice from the sidelines (he's weakened health could make him a liability on the field) and also try to make peace with himself in the remaining time he has left. Of course, he's the main character, so he gets a last minute save by a miracle cure at the end of the season.
Played for Laughs in Friends when Phoebe's psychic friend tells her she will die in three days, making Phoebe distressed and trying to do everything she can to enjoy her last few days alive. Then it turns out the psychic read her cards wrong and she was the one who was supposed to die instead.
The Patient in The Black Parade by My Chemical Romance. This is particularly apparent in "Dead!", "Cancer" and "Sleep".
"I'm still young but I know my days are numbered" is the opening line to the Crash Test Dummies "Won't you come to my funeral"
The Bee Gees' "I've Gotta Get a Message to You" was about a man on Death Row.
I've just got to get a message to you, hold on, hold on. One more hour and my life will be through, hold on, hold on.
In a series one episode of The Ricky Gervais Show Karl discusses the invention of a watch that counts down how many days a person has left to lift. When it reaches day three, it tells the wearer to visit a doctor.
A 2010 Berlin performance of Bertolt Brecht's The Rise and Fall of the City of Mahagonny toys with this. In the original play, two characters die from sheer decadence: one by overeating and one by losing a boxing match. In the 2010 performance, the stage directions were projected onto a screen and often ignored or even protested by the characters, following Brecht's philosophy of "Verfremdung". So when Jacob sees that the stage directions say he has to die, he first starts protesting, then laughing, then whimpering, then falls over helplessly and stays there for the rest of the act while other characters are swimming in money around his corpse. He's joined by the boxer character (Joe) soon after. The performance is... unsettling.
The main plot of the play Send Me No Flowers is about a hypochondriac man who overhears his doctor on the phone, and ends up believing that he has days to weeks to live. Hilarity Ensues as he then starts preparing for his death, even trying to set his wife up with another man so that she will be cared for when he's gone.
Raquel Applegate from Wild ARMs 4 is said to be suffering from a terminal illness throughout the game (and, indeed, dies in the ending). She's still a massively strong fighter in spite of this fact.
The video game Persona 3 plays this very straight and extraordinarily well with a pair of characters. One of them, the Sun Arcana Social Link character Akanari is doomed to die of a genetic disease, and uses your character and a short story he is writing to come to terms. It is implied, and later proven by the Social Link post-script ending, that he died the very day he gave you his notebook, and his mother comes to speak to you on his twentieth birthday. The other character is Ryoji, a transfer student who appears in the last few months of the storyline to give you the opportunity to kill him and live in ignorance until The End of the World as We Know It. He is doomed regardless, but wishes you "good tidings in the New Year" if you spare him, hoping against hope that you manage to somehow beat Nyx.
Also notable is Chidori of Strega, who says that she has known the day she would die for a long time. She ultimately ends up giving her life to save Junpei after he is shot and nearly killed by Takaya. In the Expansion PackPersona 3: FES, however, it's possible to bring her back.
Heck, Persona 3 has so many examples it's not even funny. There's also Shinjiro Aragaki, who knows he's only got a limited amount of time left to live because of the adverse affects of the Persona suppressants he's taking. He ultimately decides to use his last days to give Ken Amada, whose mother he accidentally killed two years ago, a chance to settle accounts with him.
In fact, during the final act of the game, when you know exactly when and how the world is going to end, the entire main cast probably qualifies. For awhile, anyway.
Just to be even more clear, the first thing the player does in game is sign a deal in which the player is "given one year." It's not exactly clear what this year refers to, and many people understand that it means "a schoolyear." Even the character who presents this contract is surprised by the ultimate outcome. But this time limit keeps hanging over the player's head throughout the course of the year...
Not so suprising since the words Memento Mori (remember that you are mortal/that you will die) can be considered to be the game's Arc Word (even though it only appears in the opening credits). In fact it can be seen as one of the main themes of the game, telling you that you will die some day so live your life while you can.
In Devil Survivor, everyone who wields a demon-summoning device can see exactly how many days are left for everyone trapped in Tokyo. Most of the numbers are quite low, and nobody inside Tokyo has more than a week at maximum, meaning it's up to you to find a way to change the future.
In Metal Gear Solid 4, Snake finds out that, due to accelerated ageing programmed into his genes from birth, he's got around 6 months left to live. Worse yet, the FOXDIE virus he was injected with at Shadow Moses, 9 years earlier, has started to mutate, and will turn him into a walking, pandemic bio-weapon within 'bout 3 months. Good motivation for One Last Mission, huh? And no pesky worrying about an exit-strategy...
Considering what Snake has lived through by the end of the game, including the absolutely soul-wrenching microwave corridor, old age is really the only thing that will stop him. And even that's debatable, since, according to a very skilled doctor, he should be dead before the game even begins. So his days might be numbered, but that number passed a while ago, and he's still going.
According to Baron Praxis in Jak II: Renegade, Jak's Dark Eco powers will eventually kill him. Jak doesn't care, because his main objective at that stage in his life is to hurl Praxis' regime to the ground, with Praxis himself preferably on fire. Despite this, he doesn't actually die in the end, because a Precursor is kind enough to counterbalance the Dark Eco effects somehow.
Lau Chan of the Virtua Fighter series has a rare illness that will eventually kill him. Still, he keeps entering fighting tournaments in search of a successor to his fighting style.
In Tales Of Symphonia, for Colette to successfully complete the journey of the Chosen, she needs to ultimately sacrifice her own life.
In Tales Of The Abyss, After Luke's heroic sacrifice at the Tower of Rem leaves him alive, he finds this out when he goes to the doctor.
Shows up in Shin Megami Tensei: Devil Survivor in impressive form. One of the functions of the COMP provides you with an uplink to the Laplace system, showing a "Death Clock" over the heads of people who have less than ten days to live. Most of Tokyo reads 7 days remaining. Your initial party reads 1, and that's during the prologue; you spend a lot of the game trying to get that number to increase.
It's interesting in that merely reading the Laplace Mail, a prediction of the future, can change the days you have remaining. For instance, the reason you start with one day is because you read a prediction where 3 people are killed in a specific place. So of course, you go and try and stop it. Turns out the 3 people who died are the ones who went to prevent it.
Actually, in that case, they wander into that one without even realizing it. The real example would be (iirc) the fight with Beldr, which is predicted to kill 50 people. So, let's go stop him! Wait, why's everyone calling him Beldr the IMMORTAL!? Oops...
In Heavy Rain, this happens if you decide to drink the poison for the fifth trial. As far as you know.
In Metroid Prime 3: Corruption, all four bounty hunters' bodies start producing phazon (Phazon is highly toxic). Eventually, Samus has to kill the other three bounty hunters, who had been corrupted by phazon. The only reason Samus doesn't get corrupted is that she destroys a load-bearing-boss on Phaaze, the source of all phazon, destroying the planet, which causes phazon to cease to exist. It makes sense in context.
Overlord Zetta of Makai Kingdom falls under The One's curse and is doomed to die in 3 days. It wasn't really The One, just a random walking Corn guy.
Note that this has no effect on the game whatsoever. It may become an issue in the third game, but Thane specifically says that while he's doomed to die, it isn't any time specifically soon.
He specifies that he has less than a year to live. Not that that really means anything, given that there's no tracking of time in the game. Could be a plot point in Mass Effect 3, though.
When the third game (which takes place half a year after the second) actually rolls around, he claims that he was given three months to live... nine months ago. In the game, he can in fact die, but from Kai Leng's sword through the chest, not from his disease.
Breath of Fire 5 uses this as a game mechanic. Your character embarks on a quest to make it to the surface - if it even exists - before his dragon counter reaches 100%. Once that happens, the dragon inhabiting him will take over and he will die. As you play through the game, the very act of walking will raise the counter by .01% every few seconds (and running will raise it faster than that.) Using various attacks in battle raise it up further and faster. If you don't play the game smart, you won't be able to finish it. At least, on your first try.
Dead Rising gives you 20 hours before you turn into a zombie after the initial 72 hours of the storymode pass by.
Dead Rising 2gives you 20 hours before Fortune City is bombed to oblivion after the military's failed attempt to contain the zombie infection.
The World Ends With You. Basically, one of the main premises of the game is that, well, the character themselves are in a game of sorts. The game lasts for a total of one week, and every day, each "Player" gets a text message with a mission for the day, after which a timer immediately (and painfully) appears on their hand. If none of the Players finish the mission before the timer runs out, the Game Master for the week officially wins, and all of the players are "Erased". However, it only takes a single pair of players (they all come in pairs, as part of the First Day's mission is to find a partner) to win for everyone to get a pass for the day. It's not always you.
Professor Layton and the Unwound Future reveals a heartbreaking twist at the end; that Claire, who was transported into the future by the experimental time machine, will very soon be whisked away back to milliseconds before the explosion that was thought to have killed her, and there's nothing anyone can do, lest they potentially cause a time paradox. Unfortunately, Dmitri tries to save her, kidnapping scientists to work on a time machine.
In Final Fantasy IX, it is heavily implied that the Black Mage golems have a set expiration date. As does Kuja.
In Final Fantasy XIII you have L'Cie brands. Once branded, a L'Cie only has a certain amount of time to complete their given focus before they turn into a Cei'th corpse (starting out as a shambling zombie-type monster, before turning into a stationary stone forced to relive their failed focus, forever). the time they have left can be tracked by the "eye" in the center of their brand, which opens as the mark advances, when it opens all the way, you turn Cei'th, this drives the party for the better part of the game. It's ultimately revealed to be averted with the main characters, the Fal'cie manipulating the L'cie heroes halt their marks after a certain point because he needs them to fulfill his Evil Plan, and wants them to have all the time they need to get strong enough to do so. And at the end of the game, they have the limit revoked completely when they succeed in their focus yet don't stay in crystal stasis, gaining "ruined" brands with no eye, much like Fang.
and in the sequel, Noel knows that when a seeress sees a change to the time-line, it shortens her lifespan. and then he realises that Serah is seeing visions. She eventually decides that saving the future is worth her life
At the start of Katawa Shoujo, hero Hisao has a heart attack and is diagnosed with a serious, potentially fatal heart condition. A big part of the Visual Novel's plot deals with him coming to terms with the fact that he could die any moment (though his condition isn't untreatable).
Reinforce Eins and the Lieze twins in Magical Girl Lyrical Nanoha As Portable: The Gears of Destiny are doomed to die in the near future and they know it. In both cases, they've accepted their fates and are trying to make the best of their remaining lives, atoning for past sins and preparing the next generation to ensure that the future is still in good hands.
One of the eponymous dragonslayers in Dragon Valor is cursed by a dragon halfling to die in a month, unless she finds and bests him in combat.
In Dragon Age, after becoming a Grey Warden, this leaves someone with only 30 years left to live due to the Darkspawn Taint running through their veins. When an older Warden senses their time is drawing near, they embark on their Calling, descending into the Darkspawn-filled Deep Roads to go out in a blaze of glory against the horde.
However, it's later revealed that the Grey Wardens are merely high-functioning ghouls, possessing the enhanced strength and stamina of the Darkspawn with a connection to their Hive Mind, but nonetheless keeping their own free-will left intact. The Calling itself is simply a ritual created by the senior Wardens so they can die as themselves before the Taint turns them into normal ghouls, who are little more than thralls to the horde.
In BlazBlue, Litchi Faye-Ling found out that she only has moments until her Boundary corruption overwhelms her and will turn her into another Arakune. Since the only one whom she knows have the cure refuse to hand it out for her, she is Forced Into Evil in order to attain the cure quick enough before it consumes her.
At the end of Super Robot Wars Destiny, provided you recruit them, you find out that ex-Ruina generals Glacies and Ventus only have 3 years to live once everything is over. What happens to them is left ambiguous, but you get the hint that they're gonna make the best out of it. When Destiny is included in Original Generations, the Destiny protagonists Joshua and Rim are trying to find out a way to extend Glacies' lifespan, and possibly Ventus' as well ('possibly' because he threw himself into the Crossgate to seal Perfectio forever so the days question might be moot inside)
Also in OG, as per her origin, Ariel Org of Real Robot Regiment only have moments in life as a result of being a product of Idealant Project. Like Glacies/Ventus, in the original game, she decided to live the rest of her life by making the best out of it, and in OG fellow Artificial HumanLamia Loveless is helping to find a way to remove that problem by reverse-engineering herself. Also, this trope is the reason why Ariel's 'rival/brother' Duvan Org becomes very power hungry and instead tried to achieve godlike power.
Parodied in Adventurers!; right before the Final Boss fight, Khrima is told this by Karn, and responds in an appropriately epic/goofy manner:
"More like...numbered to infinity! For my number will continue to increment! The only number of consequence is your chance of beating me! And that's ZERO!"
In Grim Tales, Grim is revealed to have been adding sand to Mandy's life-hourglass in order to extend her life. On the other hand, Billy's own life-hourglass looks like someone hiccuped while blowing the glass. Lots of times. And there's sand everywhere in it.
Belkar Bitterleaf in The Order of the Stick. The Oracle mentions that he "should savour his next birthday cake", along with several other less than subtle hints, surprisingly early on, but everyone forgets it due to the spell ensuring they only remember the predictions they paid for. The Oracle later gives Roy's ghost an official prediction (carefully worded to avoid Prophecy Twist, not that this stops fans who don't want to accept the Belkster's impending demise from trying) that he will "take his last breath - ever - before the end of the year", of which there are less than seven weeks left. There's no way of knowing how many strips that means, however.
In the Enthalpy episode "Robot Pilot; Or, McDarnold's La Verite", Charles is told that he will die in three hours because he ate a rotten burger. Charles uses his time to try and exact revenge on the restaurant he bought the burger from. Played for Laughs, in this case.
In the KateModern episode "The Confession", Griffin reveals that he injected fifteen girls with a serum that has had the side effect of slowly killing their immune systems, meaning that they will die in a few months time. Charlie, Kate, Julia, Steve and Terry attempt to track them down, but all are either missing or dead by the time they reach them, with one exception, Lauren. Following the events of "Precious Blood", Lauren is currently being kept alive only by taking a variety of pills daily for the rest of her life, as revealed in "The Drugs Do Work".
Survival of the Fittest: no matter which way you cut it, all but one of the students on any of the islands are subject to this trope - and even the guy who isn't won't be found out until right at the end. Additionally, pretty much every character except the most arrogant ones goes into the game assuming they're going to die.
In the Whateley Universe right now, there's an interesting variant. A young wizardess is trying desperately to avoid the consequences of an unstoppable curse. The variant? Said wizardess is the villainess Hekate, and the heinous curse was put on her by Fey, who is supposed to be one of the good guys.
Toki, a heart-breaking example, was the victim of this while she was ill leukemia in this story and another . Both instances are the same but, the latter story omitted one thing and that was that she was being severely abused and was neglected, leading to her days being formally numbered and the amount of time she was given was only a few weeks, proving the extent of her illness.
In an episode of The Venture Brothers, Dr. Orpheus is accidentally shot by Action Man. When everything is resolved, he grabs his hands...
Dr. Orpheus: Two years, seventeen days.
Action Man: ...what?
Dr. Orpheus: From a stroke. Good day, sir!
One of the episodes of Hey Arnold has Grandpa Phil dreading his 89th birthday since his family is "cursed" to die at that exact age. Even though a doctor's check-up shows that he's capable of bench-pressing more than 200lb. he constantly talks about how he's doomed to die. The episode ends with Arnold pointing out that his relatives all died when they were 99, meaning that Phil's at least got a good 10 years before he needs to start worrying.
This is a major plotpoint in the Futurama film "Bender's Big Score." Lars, despite being in love with Leela, breaks up with her because he is actually a time paradox-created clone of Fry who went back in time and lived an additional 12 years in the past before returning to the 3000s. After learning from Professor Farnsworth that all the time paradox clones will die in order to correct history he ended his relationship because he wanted her to be spared the grief of his eventual death. It comes to pass at the end of the movie when he dies via Heroic Sacrifice.
You and everyone else who is currently alive is doomed to die someday. You might be able to delay the day of your death, but there is no way to avoid it. Entropy will always win. This applied to everyone who is now dead as well.
Those involved in networking know that packets have a variable set that is decremented when it hits each point, designed to keep packets from endlessly roaming the Internets like lost souls. What's this value called? Time To Live. It dies at 0, naturally.
Dying from real life radiation poisoning can fit this trope. If you receive a potentially lethal dosage, you'll initially get very sick (headache, vomiting, fever), but then apparently recover, usually within 48 hours. However, this only lasts for a time and, after a latent period where you feel mostly fine (sometimes called the "walking ghost" phase), your condition will suddenly deteriorate with symptoms such as hemorrhaging, internal bleeding, and your immune system collapsing. The kicker is that the latent period can last up to a month, and while there are treatments that can help, the mortality rate (depending on dosage) is still very high. If you receive a dosage between 2 and 6 grays (and you're diagnosed), you'll be spending between a week and a month knowing that while you're fine now, you won't be soon, and that even with treatment there's up to 50% chance you'll die. Dosages higher than this have shorter latent periods and quickly move towards 100% mortality rate.
Living with any sort of degenerative or terminal illness.