There is no such thing as a word for "1700s" in most European languages.

Also in English it sounds weird, as you have to pronounce it "seventeen-hundreds" whereas the correct pronunciation is "one-thousand-seven-hundred". So 1700s is unsuitable for formal writing or speaking and doesn't map naturally to most languages of Western civilization.

But yeah, I guess the author finds it hard to subtract 1 in his mind :) I could go off about the typical US-centric arrogance that I see on this site, but I think it's already pretty funny as it is.