Writers Cannot Do Math / Fan Works

• In Light and Dark The Adventures of Dark Yagami, a "sevensome" goes on between six people: Sayu, Misa, Dark, Light, Light's mom and the girl from the bus.
• Child of the Storm skirts the edge of this, despite Word of God stating that he was trying very hard to make sure that everything lines up. While he apparently knew he was going to make Carol Danvers the great-granddaughter of Steve Rogers and Peggy Carter early on, he only realized rather late that he was trying to squeeze one generation too many into a ca. 60 year time period. It more or less works anyway, but even so...
• Exploited in George Weasley and the Computational Error. Because J. K. Rowling is lacking in math skills and the fandom universe knows it, the story ignores those errors as a matter of course. Thus, it assumes that an extra duplicate (such as a long-range time traveler) of someone with a previously known duplicate (such as someone with an identical twin) running around is a computational error, not something to worry about.
• One of the few such mistakes in Dead Garden occurs when Mizuki is revealed to have been a former genin teammate of Sakura's father Takeru and well acquainted with her mother Amaya. In-canon, Mizuki is a colleague of Iruka and could be no more than a few years older than him at most. When Sakura was born (and her mother died), Iruka (and by extension Mizuki) was still a kid in the Academy. Since genin teams are made up of kids from the same graduating class, or at least roughly the same age, the two facts do not add up.
• This is the case in the Gensokyo 20XX series. Amoridere isn't very good at math (she's noted this herself), explaining why the passage of time is mostly measured in months rather than years (e.g. "A few months passed") — never at all giving the exact numbers, and mostly going on Comic-Book Time. This can be seen with the ages of the children, which is rather complicated:
  • Reimu's age-regression age is currently either seven or eight and she was supposed to be three (if not four) during the events of Gensokyo 20XXIII and 20XXIV. It is noted that two years have passed between 20XXIV and 20XXV and Reimu's age-regression age then was supposed to be either five or six, which would probably make Yume Ni four and An three. This all leads one to question: exactly how many years have passed in Gensokyo 20XXIV?
  • Regarding Yume Ni, this is especially hard to figure out. It is known that Yume Ni was born some time before the nuclear war and the resulting winter, whereas An was born some time during the nuclear winter. This is referenced in-universe where Ren states that Yume Ni and An were two and three, when they are likely to be older than that and Reimu's age-regression age is stated to be either seven or eight. Thus, the best one can say is that their ages are vague.
• In Kill la Kill AU, this is averted given that the kids' ages are correctly stated. Satsuki is eleven, making her two years older than Nui, who is nine, which in turn makes her a year older than Ryuuko, who is stated to be eight. However, one would have to wonder how old their parents are, seeing that Ragyo's mother's hair is grey when we first encounter her.
• The Ace Attorney fanfic Her Life or Mine gets about every canon date or relative age wrong.
  • The fanfic takes place within "15 months" between the Hazakura case ^Note last case of third game and Phoenix's disbarment ^Note backstory of fourth game and supposedly starts in 2005. Both those canonical incidents took place in 2019, and there cannot have been 15 months between them.
  • James, an Original Character, makes several statements which play loose with character ages:
    • He mentions that Maya is a year older than him and that he was 15 during the events of the first game. During the first game Maya was 17.
    • He also claims that Pearl was eight during said events. Pearl was in fact eight during her first appearance in the second game, which canonically takes place a year after the first one.
    • He says that Dahlia is about seven years older than him. Then, one sentence later, he says that when they met for the first time, he was 11 while Dahlia was 15. Neither age gap matches canon, as Dahlia would be 23 during the first game, so eight years older than James.
• In Cellar Secrets This initially was the case with Satsuki — the story stated that she was 21, when actually she was 20. This came from the author miscalculating 17.5 + 2.5 and thinking it added up to 21, when it actually added up to 20. The mistake was subsequently corrected.
• Another Ace Attorney fic, The Fated Turnabout takes place in 2018, and Lyn goes on a date with Larry on Sunday, April 18th. That date in 2018 was a Wednesday.
• In Boys und Sensha-dō!, Miho is once described as "an eighty kilo girl." Eighty kilograms is about 176 pounds, significantly heavier than an average teenage Japanese girl like Miho, who's only 5'2" and is of average weight.
• In Boys do Tankary?, the protagonists become very concerned when the 4B3TT3RL1FE program enters the Tank Factory Invitational for the prize — a million dollars worth of tanks. $1 million is not nearly enough for a single modern MBT.
• It took A.A. Pessimal a good few tries to estimate the total number of students at the Assassins' Guild School in Discworld, with the unstinting aide of readers who corrected the maths and made wise suggestions.
• In the epilogue of The Chronicles of Tanya the Holy, Thrall mentions the Horde numbering in the millions. When the Orcs fled to Kalimdor, they only stole a few ships and even though they were joined by the Darkspear Trolls and the Bloodhoof Tauren, their numbers would realistically only be a few thousand at best.
• The Bolt Chronicles: Applies in universe to an unnamed fictional fanfic author at the TV-Con in "The Paris Trip." A poster advertising a tag-team fanfic reading includes a Bolt and Penny smut story series described as a self-styled "four-part trilogy."
• In Christian Humber Reloaded, Vash goes on a rampage at Super Bowl XXXXXII^note should be LII and kills all six million people there, including the police who showed up. In reality, Super Bowl attendance is usually less than 100,000 people, and there's no way six million people would fit into the stadium.
• Total Drama Do Over:
  • There's some inconsistencies with ages in later seasons, particularly Pahkitew, which gives canon ages for all the contestants, with each cast member being either 17 or 18 during their respective debuts. However, both previous episodes ("Back to Drama" has Gwen note that they're all high school juniors, and "Suckers Punch" has Cody refer to himself as a junior in a legal context, but both characters should be at least 19 years old by then) and even a later episode (in "Malfunction Junction," Charlotte strongly implies she was sixteen when she met Trent) contradict this information, instead implying that they were 16 at their debut as they were in the canon series.
  • In "Subzero Heroes," Abigail is said to have been born January 1996, while Colton was born December 1997. Noah claims this means that Abigail and Colton can't share a mother since they didn't have nine months between their births, but the math actually means Abigail is almost two years older than Colton, not less than two months. It's possible that the birthdates were supposed to be switched, and Abigail is meant to be born December 1996 while Colton was born January 1997.
• Arc Corp: One of the first items Jaune tells Blake about after he hires her (or rather, hires herself) is a camera that ages the user one minute per picture. He got it off a 19-year-old photographer that had aged themselves 61 years. For that to happen, the young man would have had to take 32,061,600 photos. At one photo per second, 24/7, that would take over a year, and one picture per minute would pretty much take the full 61 years in real time anyway; the writer admitted to not thinking about the math when it was later brought up. A user on his forum would later suggest that the camera should have a video function as a quick fix (at 60 frames per second, the math works out to around 6 days of continuous filming), which was incorporated into a later chapter.

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