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May Day, 1 May, is a celebration of spring and labour. In Finland, May Day is celebrated in many different ways. People gather for picnics. Doughnuts and sima, a drink similar to lemonade, are enjoyed on May Day. Many also celebrate with sparkling wine. Homes are decorated with balloons and streamers. It is customary for those who have graduated upper secondary school to wear their white caps. Labourers organise May Day marches.
Source: Info Finland
May Day (Vappu) in Hämeenlinna: Vappu Hämeenlinnassa – Hämeenlinna (hameenlinna.fi)