The period from May 12 to May 15 was noted to bring a brief spell of colder weather in the Northern Hemisphere under the Julian Calendar. With the change to the Gregorian Calendar, however, the equivalent days would be May 19-May 22.
The communists needed a day to meet and celebrate the Haymarket martyrs, and Joseph Dietzgen decided to pick the first of May.
May day is a eroupean fesitval and hold on may 1. But i am not sure about the parade, i think maay 1 day tooo!.
ya may day is nothing but which is celebrated on may 1st