2011 year marks the 100th anniversary of International Women’s Day. The day was commemorated for the first time on 19 March 1911 in Austria, Denmark, Germany and Switzerland, following its establishment during the Socialist International meeting the prior year. More than one million women and men attended rallies on that first commemoration.
In 1975, during International Women's Year, the United Nations began celebrating 8 March as International Women's Day. Two years later, in December 1977, the General Assembly adopted a resolution proclaiming a United Nations Day for Women's Rights and International Peace to be observed on any day of the year by Member States, in accordance with their historical and national traditions. (Source http://www.un.org/womenwatch/feature/iwd/)