International Women’s Day marked its 100th anniversary in 2011.
The anniversary refers to the first large international observances held in 1911, not simply to the 1909 “Woman’s Day” organized by the Socialist Party of America in New York. In 2011, events in more than 100 countries commemorated a century of international observance.
The movement developed from labor and socialist campaigns for women’s voting rights, workplace equality, and political participation. The first widely recognized European celebrations took place on 19 March 1911 in Austria, Denmark, Germany, and Switzerland, drawing more than a million participants.
A common mix-up is the date 1975: that was when the United Nations began officially observing the day. The UN’s formal recognition came in 1977, so those dates mark UN involvement—not the centenary of International Women’s Day itself.