I find that whenever such predicition is made in an ancient text, people let their imagination run wild. There was a tv show called "first wave". Its basic story line was that Nostradamus predicted that earth will be destroyed by 3 giant waves, and our hero goes around trying to stop the first wave. The premise was that the aliens were the ones to attack earth. Many times, the expected first wave would turn out to be not the real one. I think it applies to the 3rd anti-christ prediction as well.