Union Day, Unity Day, Unification Day are all days that are observed by nations most commonly to celebrate independence or a union of their country. It often celebrates a turning point where the nation or a group of people came together and unified for the country or for their cause. It also can be a day where regions celebrate unity and peace among a group of people.
About National Day
Countries around the world observe a National Day to celebration the nationhood of the country. It is most often a federal public holiday that brings out the pride in the nation.