Which body first fixed International Women's Day as March 8 in 1921?

The Second International Conference of Communist Women first fixed International Women's Day as March 8 in 1921. The decision connected the date with the Petrograd demonstrations that began the February Revolution in 1917.

International Women's Day originally had no universally fixed date. Socialist women proposed an annual observance in Copenhagen in 1910, and early celebrations occurred on different days, including 19 March 1911 in several European countries. Russia observed the day in February according to its Julian calendar.

At the 1921 conference, a Bulgarian delegation called for one common date across countries. Alexandra Kollontai, representing the Russian Soviet republic, proposed March 8 to commemorate Petrograd women’s 1917 demonstrations, and the proposal was approved unanimously. The United Nations later helped popularize the observance globally, but it did not establish the date first—a frequent quiz mistake.