It's important to remember...
...May Day wasn't invented by the Bolsheviks, it's been the traditional Day of the Worker since the 19th century, and has a history that goes back to Pagan Europe. It's association with labor and the worker has long been, and still is, celebrated in many countries, most of which never have been members of the Soviet bloc.
Throughout most of the world, May Day is the true Labor Day, and plays a similar function to the one we celebrate in September. In fact, I've always wondered why we celebrate this holiday in the late summer, instead of spring, when tradition and history have already provided a perfectly good time for working men to take a day off and throw a party.