May 30

The Ford Motor Company signs a "Technical Assistance" contract to produce cars in the Soviet Union, and Ford workers were sent to the Soviet Union to train the labor force in the use of its parts. Many American workers who made the trip, including Walter Reuther, a tool and die maker who later was to become the UAW's president. Reuther returned home with a different view of the duties and privileges of the industrial laborer - 1929
In what became know as the Memorial Day Massacre, police open fire on striking steelworkers at Republic Steel in South Chicago, killing ten and wounding more than 160 - 1937
And this:

May 30, 1937 - At the Republic Steel plant in South Chicago, police attacked strikers, killing 10 and wounding 100. Many were shot in the back. The event became known as the “Memorial Day massacre.” A subsequent Congressional investigation, led by Wisconsin Senator Robert LaFollette Jr., found the brutal suppression was unprovoked and exposed the extent to which companies would go to bust unions.
The Ground Zero cleanup at the site of the World Trade Center is completed 3 months ahead of schedule due to the heroic efforts of more than 3,000 building tradesmen & women who had worked 12 hours a day, 7 days a week for the previous 8 months – 2002
Labor history found here:
http://www.unionist.com/today-in-labor-history & here:
http://www.workdayminnesota.org/index.php?history_9_05_30_2011