This state holiday is always celebrated on 26 December. In Slovenian, it is known as 'Dan samostojnosti in enotnosti'.
This holiday commemorates the official proclamation of results of the Slovenian independence referendum (known as the 'independce plebiscite') on 26 December 1990.
The results showed that an overwhelming 94.8% of voters (88% turnout) favoured the establishment of an independent and sovereign nation.
Slovenia was one of the six republics that formed Yugoslavia from 1944 until 1990.
Until 2005, the holiday was simply called Independence Day. 'Unity' was added in 2005 to emphasise the national consensus at the time of the 1990 referendum - DEMOS, a coalition of several parties won the first free multi-party elections in Slovenia in 1990, hastening the act of independence.
The change in the name at least helped to reduce any potential confusion between Slovenia's Independence and Unity Day and Slovenia's Statehood Day, which is celebrated annually on 25 June and commemorates the declaration of Slovenian independence from Yugoslavia in 1991.