1 Alvissa: Why's the sun lower in the sky than in Footcrag? Is Cragfoot further north?
1 Villager: Ah, no. Closer to winter.
1 Alvissa: Huh?
2 Villager: The teleport gate connects the villages a fortnight apart. Going to Footcrag you go forward in time. Coming here you go back a fortnight.
3 Alvissa: Isn't that confusing?
3 Villager: Nay, it evens out.
4 Villager: 'twould only be a problem if you crossed the Orcrift Mountains on foot. And who'd be stupid enough to do that?

Living in Australia, fortnight is a completely normal, everyday word, used frequently in everyday conversation, by pretty much everyone. Many things happen on a fortnightly basis, perhaps most importantly for many people: being paid.

So it's always strange when the topic comes up while conversing with Americans, for whom the word "fortnight" is either unknown, or considered unusual, quaint, and archaic, and the fitting basis of linguistic/measurement jokes which, because to us (and citizens of many other Commonwealth countries) "fortnight" is so very normal, fall completely flat.

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2020-04-05 Rerun commentary: A reverse example which I learnt recently is the American word cater-corner, which (along with its many variant spellings and forms, including but not limited to: catercorner, catty-corner, kitty-corner, caterwampus, kittywampus) apparently means "diagonally across from". As in "my house is cater-corner to the park", meaning "my house is diagonally across from the park".

This word sounds weird, quaint, and archaic, and I honestly have difficulty believing that regular people use it in normal conversation, but I must presume that to many, if not most, Americans it's perfectly understandable and normal.

Australian (and I presume British) English doesn't even have a single word for this concept of "diagonally across from". I can absolutely guarantee you that if I used "cater-corner" in conversation with people here, nobody would have any idea what it means (except a couple of my friends, with whom I've specifically discussed this word).