Both Labor Day in the U.S. (the first Monday in September) and the International Worker's Day (or May Day, May 1st) seem to have sprung up almost simultaneously in the 1880s. The U.S. Department of Labor says that the first Labor Day holiday was celebrated on Tuesday,
September 5, 1882.
The movement in Canada may have been a little out in front of the U.S.:
"Labor unions existed in Canada in the early 1800s but legislation was adopted to make it illegal for workers to form unions…. At the beginning of May, thousands of workers and their families would
march peacefully through the city streets into the parks where they
would enjoy picnics, and listen to speakers talking about working
together to force employers to reduce working hours…. In 1872, the Canadian government changed the law so it was no longer illegal to be a member of a trade union."
Martyred Communist Rosa Luxemburg wrote that the Americans were also behind May Day:
"The happy idea of using a proletarian holiday celebration as a means to attain the eight-hour day was first born in Australia" in 1856, she wrote, and "The first to follow the example of the Australian workers were the
Americans. In 1886 they decided that May 1 should be the day of
universal work stoppage."
Ms. Luxemburg never got round to how Labor Day moved from May to September, and it's a good question, since today some 80 countries celebrate Worker's Day on May 1st. Here is Britannica's answer:
"In 1889 an international federation of socialist groups and trade unions declared the date of May 1 as Workers’ Day to commemorate the Haymarket Riot in Chicago (1886). Five years later, U.S. Pres. Grover Cleveland,
uneasy with the socialist origins of Workers’ Day, signed legislation
to make Labor Day—already held in some states on the first Monday of
September—the official U.S. holiday in commemoration of workers. Canada
followed suit not long afterward."
So, both Americans and Canadians celebrated a holiday with a day off last weekend. Montrealers were out in unusually warm weather for a street festival in Old Montreal. Here are a few HDRs. Click them to make them bigger: