Below are the salient points about International Labor Day, (click on the link here to get the website).  International Labor Day is recognized around the world, I first experienced Labor Day in France, 1982, when even the TV broadcasts didn't come on except from 5 to 6:30 pm!! 

However, I had to come to China and chat with a colleague from St. Louis who teaches Labor History to hear of the origin of International Labor Day!  The issue of Labor during those days was the 8 hour working day:

Haymarket

By Samuel Yellen

"... an excerpt from American Labor Struggles: 1877-1934 by Samuel Yellen. The chapter is titled "Haymarket," and describes the working-class mobilizations of May 1886, and the subsequent ruling-class reaction. The Federation of Organized Trades and Labor Unions- the forerunner of the American Federation of Labor- had called for strikes and mass actions beginning May 1, 1886, demanding the eight hour day.

On May 3rd, police attacked a Chicago rally supporting the eight-hour day, killing at least four pickets at the McCormick reaper plant, where 1,400 workers had been locked out for many months (described below). A demonstration called for the following evening at Haymarket Square was attacked by cops. A dynamite bomb was thrown into the police ranks by an agent provocateur, killing seven cops, and the police opened fire on the crowd. Four workers were killed, with others injured. Almost immediately every prominent labor leader in Chicago was arrested. Eight men, all anarchists, were framed up for murder and convicted without any proof. Four were hanged and one committed suicide before his scheduled execution; the others were pardoned in 1893. This was the origin of May Day as an international workers holiday. American Labor Struggles is copyright 1936 by Sam Yellen. Reprinted by permission from pathfinder press.

I have found varying accounts including the pardon by the Governor of Illinois in 1893.  Furthermore, it was not until 1935 before an 8 hour day was the law.  An interesting part of Americana.  (There is a link at the bottom of the above article to find a more sympathetic view of Haymarket.)