The various "parts" of the real-time engine use different time references to determine when things should happen. The farm and the fire use a different timing reference than the gong and Island Events do. That's why you see things returning to normal at different rates.
You shouldn't need to delete your games, though. If you set your clock back by 3 weeks, then everything should return to normal in your game once you reach the date and time that it was before you changed it. The game still thinks it's in "the past," as far as the gong and Island Events are concerned. Once time "catches up with itself" (so to speak), all should be well.