In the French Revolutionary Calendar, today, May 4, 2019, was Quintidi 15 Floréal, the 225th day of year 227 of the revolutionary era—as in the French Republican Calendar. Today was also the 48th day of the Paris Commune in 1871. Here in New York, the local bourgeoisie feared a New York City Commune. This is detailed in Chapter 57 of Gotham (1999), by Mike Wallace and Edwin Burrows. Had this NYC Commune taken place we would most likely note have moved the working class commemorative day of struggle known as May Day to the first Monday in September as was done here in the US. May Day began as a result of the Haymarket Massacre which took place on May 4, 1886 in Chicago, and the executions of eight innocent anarchists for incitement to riot and murder as a result of the 11 deaths that day.
On libcom.org you can find biographies of the eight working class martyrs: http://libcom.org/history/autobiographies-haymarket-martyrs
May 4, 1886: Haymarket Massacre
A huge rally gathers, demanding an 8-hour workday. A bomb is thrown as Chicago police start to break up a rally for strikers at the McCormick Harvesting Machine Co. A riot erupts, 11 police and strikers die, mostly from gunfire, and many more are injured in what was a police riot.
Other May 4 events in US history of significant importance.
1961: Freedom Riders
The Freedom Riders begin a bus trip through the American southern states of Jim Crow. The Klan and other southern racists attack the Freedom Ride Greyhound repeatedly, eventually setting it on fire attempting to burn alive the bus Freedom Riders.
1970: Kent State Students Murdered by Ohio Governor and National Guard
The Ohio National Guard, sent by Ohio Governor Rhodes to Kent State University after protests in the city of Kent the weekend before because of the US invading Cambodia, opens fire murdering four unarmed students and wounding nine others. Each year anti-imperialist Americans and others gather to remember those who lost their lives. This was a pivotal moment in the anti-war movement, and led many who had wavered before May 4, 1970 into the anti-ware and many of those into anti-capitalist movements to this day.