May 1 is Labour Day in most European countries, except in The Netherlands. Here we celebrate the Queen's birthday on April 30 (which was Queen Juliana's birthday. Beatrix -- our current Queen -- was born on January 31, but when she became Queen it was decided to keep celebrating Queen's Day on April 30, because January 31 would be too cold for most outdoor activities on this Dutch national holiday).
So we celebrate while the rest of Europe is working, then start working as (most of) the rest of Europe has a holiday. One of the many ironies in the EU.
Personally, I'd prefer to celebrate Labour Day, even though my mother was just decorated. I rather celebrate the achievements of workers than that of one of the richest royal families in Europe. Red above Orange!