This day is celebrated over 21st and 22nd May to celebrate the anniversary of the Montenegrin independence referendum in 2006 when the country decided to leave Serbia and Montenegro.
It was renamed Serbia and Montenegro in 2003 under the Belgrade agreement after formerly being named the Federal Republic of Yugoslavia. This contained a provision that any referendum on Montenegro would not take place for three years. It was held in 2006 with an 85% turnout, with 55.5% voting in favour of independence. It declared independence on 3rd June 2006.