Independence Day is an annual holiday celebrated in countries around the world commemorating the anniversary of the nation's independence. Each country has it's own reason to celebrate and many are celebrated similarly under other names such as National Day, Foundation Day, Statehood Day or name the day for their country.
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.
Unity Day celebrates the reunification of Federal Republic of Germany and Democratic Republic of Germany in 1990. The two parts had been separate since the end of World War II. Though it is a relatively new holiday in Germany, it is one of the most important days as it represents the identity of the country today. It is celebrated much like Independence Day and National Day in many other countries with public festivities such as fireworks and parades, and an overflowing abundance of national pride.