"51" International Day referred to as 51, in the May 1 each year. It is the common working people around the world holiday. On "the origin of 51" is like this:

    This section from the U.S. strike in Chicago. May 1, 1886, Chicago, more than 20 million workers to fight for the implementation of an eight-hour working day strike held, after a bloody hard struggle, finally won victory. To commemorate the labor movement, July 14, 1889, convened by the Inter-Marxist socialists Congress opened in Paris, France. The General Assembly, the delegates agreed that: to May 1st as the international proletariat, the common festival. This resolution received a positive response from workers in countries around the world.

    Hereby Boyu wish all labors a good day.