Today is Labour Day in France, known in French as La Journée du Travail. It is also being celebrated all over Europe (except for Switzerland and the Netherlands). In France it is also known as La Fête du Muguet, a celebration that dates back to the Middle Ages. Muguet is the plant we call Lily of the Valley in English, and the Celtic people accorded this plant with the property of a porte-bonheur (good luck charm). In 1561 Charles IX formalised the custom of donating a bunch of the flowers to one's friends and family, when he gave a bunch to ead of the ladies in his court. The flower is also associated with lovers who exchange them on this day (no Lucas and I didn't wake up early enough to go buy each other fresh bunches).
The same holiday is also being celebrated around the Caribbean, and probably throughout the British Commonwealth. We call it May Day. The actual day on which it is celebrated differs from island to island. In Barbados like in Britain it is celebrated on the first Monday in May, whereas in other islands it is always the 1st of May. This is the day in Barbados when the big Trade Unions have marches and rallies for their members.
From the information I was able to find online it would appear that many of the other traditions we have on this day, such as dancing around the May Pole and Morris Dancing, originated in England and date back to the pagan festival of Beltane.