National day

National days are the days which are very special and important for a nation. A National day is a special day where people celebrate their country or nation each year. Most countries have national days and they are usually a national holiday, where people don't go to work or school. In many countries which used to be colonies, the national day is known as because it remembers the day they became free of their old empire. In other countries like China, the national day remembers when the old government of the country changed to the new one. In the past, the king or emperor's birthdays were often treated as a kind of national day. 
Most countries have only one national day each year but some (like India, Bangladesh and Pakistan) have more than one. The different parts of the United Kingdom used to be separate independent nations and still have national days, but the UK does not have one holiday for the whole country apart from the Queen's Official Birthday. (This isn't her real birthday or an official holiday, but a special Saturday to remember her when people are usually already off work anyway.) Denmark is another country that has no official national day.