History Main / AgeGapAlgebra

* In ''Manga/FourKnightsOfTheApocalypse'', Guinevere's EstablishingCharacterMoment is sexually assaulting a boy four years older than her (Guinevere is '''[[FilleFatale twelve]]''') and trying to convince him it's okay with this trope. He's not into it. They ''do'', however, start dating three years later.

* Creator/AbbottAndCostello had a routine where Costello claimed he was 25 and had [[{{Squick}} fallen in love with a five-year-old]]. Abbott suggests if Costello waits five years, he'll be three times her age instead of five times. Abbott then suggests if Costello waits ten years more, he'll only be twice her age. Costello asks Abbott how long until he and she are the same age.

[[folder: Comic Books]]
* This is used to justify Bruce Wayne having a relationship with Superman's granddaughter (who is his own granddaughter by adoption) in the far-future sections of ''Comicbook/SupermanAndBatmanGenerations III''; both being past 400 years old makes them basically "the same age".

-->'''Marianne:''' But thirty-five has nothing to do with matrimony.
-->'''Elinor:''' Perhaps thirty-five and seventeen had better not have any thing to do with matrimony together. But if there should by any chance happen to be a woman who is single at seven and twenty, I should not think Colonel Brandon's being thirty-five any objection to his marrying HER.

* In a ''Series/StudioC'' "James Bond" sketch available only on the Creator/BYUtv website, Bond tells his partner that she won't make it in the next movie because of her age. (she's almost 30) He then iterates the "rule of seven" to her ...but with a very ''unsettling'' twist.

[[caption-width-right:216:Numbers don't lie! (Ironic)]]

Though not being considered exactly an issue or a thing in the past, one common criterion for compatibility between prospective marriage or romantic partners today, or at least created recently (relatively speaking) in an unspecified time and unsupported except by public perception (particularly in the West), is the difference between their ages. This trope is when a specific formula or calculation is proposed to determine either the "ideal" (?) age difference or the maximum allowable (?) age difference before it becomes "creepy". This is [[https://en.m.wikipedia.org/wiki/Ageism fortunately recognized as a bigoted ageist trope, and also illegal in real-life society depending on the circumstance, like slander/defamation, harassment and/or incitement to hatred or hate speech]].

[[caption-width-right:216:Numbers don't lie!]]

One common criterion for compatibility between prospective marriage or romantic partners is the difference between their ages. This trope is when a specific formula or calculation is proposed to determine either the "ideal" age gap or the maximum allowable age gap before it becomes "creepy".

* In ''Series/ParksAndRecreation'' Andy (29) asks [[CasanovaWannabe Tom]] how young is too young to date. Tom quotes the half-your-age-plus-seven rule, which, in Andy's case, would be 21 and a half, causing Andy some consternation when he realizes this technically puts the 21-year-old April in the "too young" range. [[TheyDo He gets over it.]] It helps the audience that the age gap between the actors is only five years instead of eight (and that [[ManChild Andy's]] mental age ''at best'' is around 21).

[[folder:Theater]]

One commonly-applied formula is the "half your age plus seven" rule, in which the older partner's age is divided by two and then increased by seven to reach either the ideal or minimum allowable age for a romantic partner. This has the advantage of allowing for a larger age gap the older the partners get; the four-year age gap between a 22-year-old and an 18-year-old is significant (and just barely allowed by this rule), but the same age gap between [[DecemberDecemberRomance an 86-year-old and a 90-year-old isn't worth comment]]. The rule would theoretically create a paradox for people under 14 because the younger partner would have to be older than the older partner, but 14 is about the youngest you can be and make anything even remotely resembling adultish decisions respecting relationships anyway, so this rule works out rather well. In its earliest appearances, this rule is often cited as having French origins, although this citation always seems to appear in English-language (British or American) sources, leaving its true origin mysterious.

[[folder:Film]]

* The MayDecemberRomance trope on Wiki/ThisVeryWiki specifies an age gap of at least thirty years before examples qualify.

* The main premise of ''Film/LiberalArts'' is about the UnresolvedSexualtension between a 35 year-old man and a 19 year-old young woman. When the male lead is contemplating having a RelationshipUpgrade with the female lead, he's seen calculating their sixteen-year age gap on a piece of paper. He only sees it as "passable" when he starts calculating the gap when she reaches her thirties.

** In a later season Ross starts dating one of his college students. He acknowledges there's an age gap and it looks as if Joey's about to do the maths for him again but this time he reaches a different conclusion.
--->'''Ross:''' I know when I’m 90 she’ll be like 80 and it won’t seem like such a big difference.\\
'''Joey:''' No that’s not what I was going to say at all. No, what I was going to say is when you’re 90 you’ll still have the memory of what it was like to be with a 20-year-old.

Traditionally, a man was expected to be established in his career and lifestyle before marriage, whereas a woman usually transferred directly from her father's household to her husband's within a couple of years of reaching adulthood, so it was considered ideal for the man to be at least somewhat older. As [[SocietyMarchesOn Society Marched On]], this became less and less the case, and in modern works a very small age gap is often considered ideal, with a maximum allowable (as opposed to "ideal") age gap proposed, and often applied equally in either direction (older man vs. older woman).

* Webcomic/{{Xkcd}} [[http://xkcd.com/314 #314]] shows the "Standard Creepiness Rule" listed as "Don't date under (age/2 + 7)", providing a minimum age if not an ideal age.

* In Webcomic/{{xkcd}}'s spinoff {{Blog/WhatIf}}, a writer asks what would happen if each person had one soul-mate and could be happy with no one else. Randall ends up using an age limit much more strict than x/2 + 7, arguing it would be creepy if a couple met as children (30 & 40 isn't so bad, 5 & 15 is a problem).

* In TheSimpsons, Lisa falls in love with a cowboy who is 5 years older than her. When Marge says that he is too old for her, Lisa points out that the difference won't matter when they are both adults.

-->'''Joey:''' Yeah, come on, think about it. You're 18, okay, she's 44. When you're 36, she's gonna be 88.
-->'''Frank:''' What, you don't think I know that?

* In ''Series/ParksAndRecreation'' Andy (29) asks [[CasanovaWannabe Tom]] how young is too young to date. Tom quotes the half-your-age-plus-seven rule, which, in Andy's case, would be 21 and a half, causing Andy some consternation when he realizes this technically puts the 21-year-old April in the "too young" range. [[TheyDo He gets over it.]] It helps the audience that the age gap between the actors is only five years instead of eight (and that [[ManChild Andy's]] mental age ''at best'' is around 21).
-->'''Andy''': April's the best, but she's 20. When April was born, I was already in the third grade, which means if I were friends with her back then, I'd have been friends with a baby. I don't know anything about infant care... my god, I could have killed her!

* TheSimpsons, Lisa falls in love with a cowboy who is 5 years older than her. When Marge says that he is too old for her, Lisa points out that the difference won't matter when they are both adults.