Delegates from 17 countries agreed to the Women's Day idea at the 1910 conference. The meeting was the Second International Socialist Women's Conference, held in Copenhagen alongside the Socialist International's congress.
About 100 delegates attended from 17 countries. Their agreement followed Clara Zetkin's proposal, supported by fellow German delegate Käte Duncker and others, for an annual day highlighting women's political and social rights.
The number 17 refers to the countries represented, not the number of delegates. That distinction matters because contemporary summaries often mention both figures: roughly 100 delegates representing 17 countries. The conference approved the concept but did not establish a fixed calendar date; early observances were held on different dates before March 8 became standard.