From the Wiki:
International Women's Day (IWD) is celebrated on the 8th of March every year around the world.
(…) The day was then predominantly celebrated by the socialist movement and communist countries until it was adopted by the feminist movement in about 1967. The United Nations began celebrating the day in 1977.
It is a federal holiday in Russia, at least. (Since it's Sunday this year, the following Monday is made a holiday as well). Do you have any special plans for today?