This holiday is pretty popular in my country, even though many people connect it with communism. I remember reading that this originated from an event that happened in the US.
What were the reasons for US having it on a different day?
And how widespread are the May 1st celebrations in the rest of the world?
While waiting for a new answer, you may be interested in this response by /u/QuickSpore to a similar question, detailing the origins of May Day and why it gained international importance.