May Day on May 1 is an ancient Northern Hemisphere spring festival and usually a public holiday; it is also a traditional spring holiday in many cultures.
The earliest May Day celebrations appeared in pre-Christian times, with the festival of Flora, the Roman goddess of flowers, and the Walpurgis Night celebrations of the Germanic countries. It is also associated with the Gaelic Beltane. Many pagan celebrations were abandoned or Christianized during the process of conversion in Europe.
A more secular version of May Day continues to be observed in Europe and America. In this form, May Day may be best known for its tradition of dancing "the maypole dance" and crowning of the May Queen.
Fading in popularity since the late 20th century is the giving of "May baskets", small baskets of sweets and/or flowers, usually left anonymously on neighbours' doorsteps.
Here you can read an interesting article about May Day as "a cornucopia of holidays" ...