How old is Charlie Weasley?
I was reading fic. I was happy. And then I decided to try and figure out the relative ages of characters, because I wanted to be able to figure out how old X is when Y is in 5th year, if Z was in 3rd year when W was born. (The alphabet goes x, y, z, w. This is an incontrovertible fact that any math major will confirm for you.)
The problem, or at least the first problem, is Charlie Weasley's age. This summarises it nicely.
Basically, we have a) Charlie Weasley was a brilliant Seeker, with the implication that there was a streak of glorious wins while he played; and b) Gryffindor hasn't won for 7 years in PoA. At first, it seems clear: Gryffindor had a Quidditch golden age while Charlie was there, and then, after his last year, the team kind of died, and Harry's first year is the beginning of its resurrection. Except Charlie can't be that much older than Percy. (According to JKR, he's 3 years older, and since she's also given us their birthdays, that's 3 years and 8 months. This is just interview canon, though, and can be ignored if necessary. Or if you just feel like it.)
Fred says, in PS, "'We haven't won since Charlie left". That's lovely - except if Charlie is 3y older than Percy, Charlie just left Hogwarts. There are three possible solutions to this: either Charlie left Hogwarts early, before his 7th year, as has been suggested, I wish I remembered where, or he stopped playing Quidditch (perhaps to focus on schoolwork?), or he's actually more than 3 years older than Percy.
But even saying, "oh, she screwed up, she's bad at arithmetic, it's more than 3y" doesn't really help. Unless you move it up to Charlie being eight years older than Percy, the two trends overlap, and the smaller the age difference, the more they overlap. It's fairly clear from the context of the books that Charlie and Percy are quite close in age - I'd say 5 years would be pushing the bounds of possibility. So in order to preserve both the Charlie-wins trend and the Gryffindor-loses trend (or at least to make it at least somewhat likely that people would remember both as trends), we need to pick one of the other two "solutions" above.
The problem with both of them is that you'd think someone would have mentioned them at some point. I tend to incline towards the second one: while Charlie wouldn't necessarily need to finish school, at least in the traditional manner, in order to work with dragons, Molly would go completely and utterly nuts if he dropped out. I suppose it's possible that there is some special school/training program for dragon-handler-wannabes, where Charlie went instead of finishing Hogwarts, but it's a big stretch. But on the other hand, given how much people care about Quidditch, would it really be likely that a brilliant Seeker and Captain would just quit?
Still, my headcanon, in the end, is this: Charlie Weasley is 3 years and change older than Percy. He got on the team in his second year, which was the last year that Gryffindor won the cup until PoA. Afterwards, though he was a brilliant Seeker, and won many matches, his team never won the cup again. (Perhaps he was fouled several times- this would certainly fit with the mentions of Seekers being fouled a lot, of which there are several in PS.) Charlie became Captain in his 4th or 5th year, and was Captain for a year or two. At the end of his 5th year, he realized that his grades were slipping because of Quidditch, and resigned from the team, as he needed good grades to get into dragon training (complete fabrication on my part, but plausible - you don't want idiots handling something as dangerous as dragons; moreover, you'd probably need NEWTs in Care of MC and DADA, and possibly Charms, Potions, and Transfiguration as well.)
The following couple of years saw the Gryffindor team hit rock bottom. In the last year, we know that Wood as a third year(!) was Captain, and that Fred, George, and Angelina played as second years, with Fred and George on either school brooms or cheap crappy brooms of their own. Whoever the Seeker and the other two Chasers were, they were not apparently very good (which begs the question of why Alicia Spinnet was "only a reserve", though several possible explanations spring to mind). This does not a good team make. This quite likely coincided with a drop of interest in Quidditch in the house, since in PS, Wood can't find a single halfway decent Seeker until Harry shows up. These two years would probably be enough of a gap between Charlie and Harry, though another year would make slightly more sense.
So, if we move Percy's birthday from late August to early September, then, in Charlie's fourth year, Percy is just slightly too young to be a first year, and, though Charlie is only 3 years and 9 months older than Percy, he is 4 school years older. This gives us our extra year without making an almost 5 year gap for Molly and Arthur. Since Percy is two school years older than Fred and George, and their birthday is April 1, he is now 2 1/2 years older than them and not 1 1/2.
Or, you know, you can just handwave it.
The problem, or at least the first problem, is Charlie Weasley's age. This summarises it nicely.
Basically, we have a) Charlie Weasley was a brilliant Seeker, with the implication that there was a streak of glorious wins while he played; and b) Gryffindor hasn't won for 7 years in PoA. At first, it seems clear: Gryffindor had a Quidditch golden age while Charlie was there, and then, after his last year, the team kind of died, and Harry's first year is the beginning of its resurrection. Except Charlie can't be that much older than Percy. (According to JKR, he's 3 years older, and since she's also given us their birthdays, that's 3 years and 8 months. This is just interview canon, though, and can be ignored if necessary. Or if you just feel like it.)
Fred says, in PS, "'We haven't won since Charlie left". That's lovely - except if Charlie is 3y older than Percy, Charlie just left Hogwarts. There are three possible solutions to this: either Charlie left Hogwarts early, before his 7th year, as has been suggested, I wish I remembered where, or he stopped playing Quidditch (perhaps to focus on schoolwork?), or he's actually more than 3 years older than Percy.
But even saying, "oh, she screwed up, she's bad at arithmetic, it's more than 3y" doesn't really help. Unless you move it up to Charlie being eight years older than Percy, the two trends overlap, and the smaller the age difference, the more they overlap. It's fairly clear from the context of the books that Charlie and Percy are quite close in age - I'd say 5 years would be pushing the bounds of possibility. So in order to preserve both the Charlie-wins trend and the Gryffindor-loses trend (or at least to make it at least somewhat likely that people would remember both as trends), we need to pick one of the other two "solutions" above.
The problem with both of them is that you'd think someone would have mentioned them at some point. I tend to incline towards the second one: while Charlie wouldn't necessarily need to finish school, at least in the traditional manner, in order to work with dragons, Molly would go completely and utterly nuts if he dropped out. I suppose it's possible that there is some special school/training program for dragon-handler-wannabes, where Charlie went instead of finishing Hogwarts, but it's a big stretch. But on the other hand, given how much people care about Quidditch, would it really be likely that a brilliant Seeker and Captain would just quit?
Still, my headcanon, in the end, is this: Charlie Weasley is 3 years and change older than Percy. He got on the team in his second year, which was the last year that Gryffindor won the cup until PoA. Afterwards, though he was a brilliant Seeker, and won many matches, his team never won the cup again. (Perhaps he was fouled several times- this would certainly fit with the mentions of Seekers being fouled a lot, of which there are several in PS.) Charlie became Captain in his 4th or 5th year, and was Captain for a year or two. At the end of his 5th year, he realized that his grades were slipping because of Quidditch, and resigned from the team, as he needed good grades to get into dragon training (complete fabrication on my part, but plausible - you don't want idiots handling something as dangerous as dragons; moreover, you'd probably need NEWTs in Care of MC and DADA, and possibly Charms, Potions, and Transfiguration as well.)
The following couple of years saw the Gryffindor team hit rock bottom. In the last year, we know that Wood as a third year(!) was Captain, and that Fred, George, and Angelina played as second years, with Fred and George on either school brooms or cheap crappy brooms of their own. Whoever the Seeker and the other two Chasers were, they were not apparently very good (which begs the question of why Alicia Spinnet was "only a reserve", though several possible explanations spring to mind). This does not a good team make. This quite likely coincided with a drop of interest in Quidditch in the house, since in PS, Wood can't find a single halfway decent Seeker until Harry shows up. These two years would probably be enough of a gap between Charlie and Harry, though another year would make slightly more sense.
So, if we move Percy's birthday from late August to early September, then, in Charlie's fourth year, Percy is just slightly too young to be a first year, and, though Charlie is only 3 years and 9 months older than Percy, he is 4 school years older. This gives us our extra year without making an almost 5 year gap for Molly and Arthur. Since Percy is two school years older than Fred and George, and their birthday is April 1, he is now 2 1/2 years older than them and not 1 1/2.
Or, you know, you can just handwave it.