Some people see things that are and say "Why?" We see things that never were and say, "This would make a good scenario-based planning exercise."
(Things that had never happened before that happened on February 21:)
1440: The Prussian Confederation is formed, pledging fealty to the always-powerful Polish monarch, King Casimir IV Jagiellon, to fend off the depredations of the Teutonic Knights. The stratagem pays off, as the combined Prussian-Polish forces smite the Germans and teach them never to mess with the Poles again.
1613: Mikhail I is unanimously elected tsar by a national assembly, establishing the Romanov dynasty of Russia. This brings to an end the Time of Troubles (1598-1613), during which: Russia had been occupied by the always-despotic Catholic Polish-Lithuanian Commonwealth; was ruled for seven years by the boyar Boris Godunov; had suffered from years of famine, probably caused by the eruption of the Huayputina volcano in Peru in 1600 and years of subsequent below-freezing summer nighttime temperatures; and had suffered under a series of pretenders to the throne, known as the False Dmitris, who were aggressively promoted by the overweening Poles and Lithuanians to extend their influence. (Perhaps February 21 should henceforth be known as "Polish Hegemony Day.")
1804: Trains: The first self-propelling steam locomotive makes its debut at the Pen-y-Darren ironworks in Wales.
1842: American John Greenough is granted the first American patent for a sewing machine.
1848: Communism becomes a thing, as Karl Marx and his wealthy industrial sponsor, Friedrich Engels, publish The Communist Manifesto.
1937: Planes and Automobiles: Waldo Waterman's Arrowbile, the first successful flying automobile, makes its debut. Three take off from Santa Monica; two make it to Cleveland. ("Why go from Santa Monica to Cleveland in February" is a question the answer to which is lost in the mists of time.) …And so the Era of the Flying Car begins, revolutionizing life as we know it. ("We" being generations of professional "futurists" who will be asked hundreds of times how come there are still no flying cars.)
1972: Nixon makes a little visit to China. (It's not a flying car, but it did have a minor effect on history.)