This state holiday is always celebrated on 25 June. In Croatian, it is known as 'Dan državnosti'.
This holiday is Croatia's national day and commemorates Croatia's declaration of independence from Yugoslavia on 25 June 1991.
Historically part of the Austria-Hungarian Empire until its collapse at the end of World War I, Croatia was one of the six republics that formed Yugoslavia.
In May 1991, the Croatian independence referendum had resulted in a 94% vote in favour of establishing an independent Slovenia.
While the declaration occurred on 25 June, Croatia celebrates its Independence Day on 8 October as following the declarations of Independence by Croatia and Slovenia, a three month period of no further independence actions was put in place to see if an agreement could be reached with Yugoslavia.
In the end, those discussion proved fruitless and so Croatia became an independent nation on 8 October 1991.
Slovenia also celebrates Statehood day on the same day, as it was also a state created from the dissolution of Yugoslavia.