As often happens, I was chatting with my French friend Cerise when she tossed in a French word that she assumed we also use in English, but in fact do not. And as is often the case, the French have a fantastic and specific word where we have but a clunky phrase. The word in this case is “uchronie”, which in English means roughly “the setting of an alternate history story.” The word is based on the Greek roots “u” and “chronos”, as in “utopia” (or un-place) and time, and therefore means “a non-time”. The concept is of course familiar to any reader of speculative fiction (generally thought of as a classier term for science fiction, but really a broader term that includes science fiction as well as things like alternate history, that never fit comfortably in the SF category) but our language lacks such an elegant word for it.
Note that the English form of this word would be uchronia, as utopia is utopie in French.