It happened today - April 4, 2016
It’s different because April 4 1147 is the first historical reference to Moscow, as a minor town on the western edge of the Vladimir-Suzdal Principality. Vladimir was the local big player in those days, and Moscow gets noted because of a meeting there between Yuri Dolgorukiy, son of the Grand Prince of Kiev and then in charge of Vladimir-Suzdal, and Sviatoslav Olgovich, a local potentate with a mixed record who was at that point apparently Prince of Belgorod Kievsky, whatever that was.
Apparently Dolgurukiy liked the place enough to give it a timber fence and moat in 1156. And the invading Mongol Batu Khan hated it enough to burn it down and massacre its inhabitants. So the Moscow that later appeared was, as sadly with so much of the area, deformed by the Tartar yoke in ways that were tragic for its inhabitants and the world.
The site of Moscow or the fort “na Moskvě”, on the Moscow River as it was known when Alexander Nevskii’s youngest son Daniel was given it as some sort of feeble consolation prize in the 1260s, had of course been occupied periodically from at least Neolithic times, as any place suitable for a village or city tends to be. But the Mongol conquest draws a sharp line between what might have happened there and what actually did.
April 4 1147 would be a much happier date without the Mongols. And that quality, too, it shares with a great many other historical dates including very recent ones.