The National Day is often taken as the date on which a state or territory achieved independence. Other dates such as the country's patron saint day, or a significant historic date are sometimes used. Most countries have a single National Day per year, though a few, for example, India and Pakistan, have more than one. Besides that, each of the two special administrative regions of the People's Republic of China, namely Hong Kong and Macao, celebrate the day of the establishment of the special administrative region, as well as the National Day of the People's Republic of China.
Most countries have a fixed date National Day, but some have movable dates. An example here is Jamaica, which celebrates its National Day on the first Monday in August. This commemorates independence from the United Kingdom which was attained on Monday, 6 August 1962 - the first Monday in August of that year. Another example is Thailand which celebrates the birthday of the King on 5 December. This date will change on the accession of the heir to the throne.