The connection between this Apocalyptic quote and "Gangnam Style" isn't exactly obvious, but with a little help it becomes clear Nostradamus was talking about KPop.
Did you know that Korea means "calm morning." Hear that? That's the sound of your mind being blown. The second line about the dancing horse is pretty obviously about PSY's now-famous dance move, and the nine circles represent the nine zeroes in the number one billion, as in "Did you hear PSY's 'Gangnam Style' got a billion hits on the same day the Mayan Apocalypse is supposed to happen? How freaky is that?" Answer: very freaky.