I haven't noticed it, too (at least the first time), but I'm ready with all sorts of excuses for the author. Goldsmith wrote hurriedly, and anyway, Dr Johnson grabbed the book and brought it to the publishers himself, not giving Goldsmith a chance to edit. I don't think 18th century writers edited much. Anyway, how unusual is time disparity in an invented world? Anna Karenina was written and re-written with all attention Tolstoy could give it, and still what comes between Vronsky and Anna takes four years, and the events of Levin/Kitty storyline take two and a half. So there! :)