Many people don't know that Goa didn't got Independece in 1947, when the whole India got free from British, Goa was still under the dominace of Portuguese.
Portuguese were the people who ruled Goa and other Indian territories for more than 450 years, even after Independence their denied to give up hold on Goa and after a decade of National Indepence, Gao got freedom from Portuguese, on 18th December 1961.
After so many attempts by the Indian government, Portuguese didn't gave up on Goa, which later forced former Prime Minister Jawaharlal Nehru to intervene the army, and after 36-hours of attack, the Indian navy, air force, and army. General Manuel António Vassalo e Silva surrender himself, and that was the end of Portugese rule in Goa. The Indian forces named this operation and 'Operation Vijay'.
That's why India celebrates 18th December as the Goa Liberation Day, because Goa got real freedom on this day. The government also celebrates this day to recognized the achievements and milestones Goa has made in recent years, Goa give higgest income on tourism amongst the country and other Union territories.
Localites celebrates this day, with events like folk dance, music, and various cultural programs.
This year Prime Minister Narendra Modi will also visit Gao on it's Liberation Day. He will attend the function at Dr Shyama Prasad Mukherjee Stadium in Taleigao at around 3pm. He will also pay tribute to Army forces and Freedom Fighters who made this Operation Vijay successful.