Here, two 15 year olds can have sex, legally. 15 year old and 17.9 year old can have sex. 15 and 18 can't, but do, because the law is demented - if you have two

Here, two 15 year olds can have sex, legally. 15 year old and 17.9 year old can have sex. 15 and 18 can't, but do, because the law is demented - if you have two partners, say 15 and 17, as they age, they will first be able to legally have sex, then for a few years they will not, until again, they will.