Things that happened on March 5 knowledge of which might spark some ideas for scenario planning:
363: Roman Emperor Julian the Apostate departs with a large army for present-day Iraq, bent on regime change. He will win a victory outside the gates of the Sassanid capital of Ctesiphon (present-day Salman Pak), but after the cakewalk, his forces are harassed and repeatedly attacked by enemy forces, and ultimately historians will conclude that he had fatally divided his armies, attacking with a level of forces capable of winning initial victory, but not enough to successfully occupy and subdue the territory.
1616: The Catholic Church bans Copernicus' book about the sun being the center of the solar system.
1912: The Italian Army is the first to employ airplanes for reconnaissance and attack behind Turkish lines in Libya. The Turks are therefore the first force ever to shoot down an attacking airplane.
1933: Adolf Hitler's party receives 43.9% of the vote in Reichstag elections, ultimately allowing the Nazis to establish a dictatorship.
1975: First meeting of the Homebrew Computer Club in Menlo Park, California. A year later, members Steve Wozniak and Steve Jobs will found Apple Computer.
1979: A powerful gamma-ray burst hits two Soviet and one U.S. solar satellites; the source is triangulated back to somewhere in the Magellanic Cloud, leading to the discovery of "soft-gamma repeaters," objects (believed to be neutron stars with surrounding fossil disks or else magnetars, neutron stars with extrmely powerful magnetic fields) that emit gamma radiation at irregular intervals.