The United Nations declared March 8 the International Women’s Day in 1975, itself the International Women’s Year, to mark the already long history (more on the history on Wikipedia) of celebration and protests.
In these parts, the tradition of activism and demands for women’s rights was replaced during the socialist system by tradition of organized partying in restaurants, bouquets of flowers and long boring conferences by the official women associations (to the effect that Wikipedia article, probably correctly, notes that it was some sort of combination of Mother’s Day and St. Valentine’s Day.