Labor Day "Protomagia" (May 1st) celerated today
The day is celebrated with a feast is called "Protomagia" (def. "first day of May"). It is an urban holiday when people traditionally visit to the countryside to enjoy a picnic.
It is also a day when large demonstrations are organized by the left political parties. Similar to the American "Labor Day", it is a day off for everyone.
Notably, in Greek mythology, the goddess of the harvest, Demeter, after the abduction of her daughter by Hades, the god of the underworld, deeply in sorrow and blinded by her anger for losing her precious daughter, all of the plants stopped growing, the flowers withered and died, and the land became desolate. While her daughter was with Hades, in the underworld, it was Fall and Winter on earth. And when Persephone returned, it became Spring and Summer.
Therefore, along with the flowering of Mother Nature, where wildflowers cover hillsides, Greek families take picnics in the countryside to celebrate and to enjoy nature itself. After the collection of the flowers, people traditionally hang wreaths out on their doors to make the entrance of the home even more colorful and happy looking.