Woman's Day, also known as National Woman's Day (a retronym in regard to the later international observance), was a commemoration conceived by labor activist Theresa Malkiel, and organized principally in New York City by the Socialist Party of America on the last Sunday in February in 1909 and 1910. It was the immediate predecessor to International Women's Day which began to develop globally in 1911, although it was still observed in the United States in February rather than in March for several years.[1][2][3]