On Sunday August 26th, people in the United States will be celebrating Women's Equality Day. It is a day to commemorate the passing of the the Nineteenth Amendment to the United States Constitution allowing women the vote in that fall's elections, including the Presidential election. The day was designated in 1971.
There is a plethora of information available from ask.com here if you are not familiar with this issue. A brief history lesson from the US Government can be found here.
The White House's official proclamation for the 2007 commemoration can be found here.