Every country has its own National Day, and the reasons for establishing this special day vary from nation to nation. Below is a brief overview of how some countries celebrate their National Days:

1. United States: The U.S. celebrates Independence Day on July 4th each year. This date marks the adoption of the Declaration of Independence in 1776, which declared the thirteen American colonies independent from British rule.

2. France: Bastille Day, celebrated on July 14th, commemorates the storming of the Bastille prison in 1789, an event that marked the beginning of the French Revolution and the fall of the monarchy.

3. China: The People's Republic of China was founded on October 1st, 1949. Since then, October 1st has been celebrated as National Day, marking the establishment of the new government.

4. India: India gained independence from British rule on August 15th, 1947. This date is celebrated annually as Independence Day, honoring the end of colonial rule and the start of self-governance.

5. Japan: Japan’s National Foundation Day is celebrated on February 11th. It marks the legendary founding of Japan by Emperor Jimmu in 660 BC.

Each country’s National Day carries significant historical importance and serves as a reminder of pivotal moments in their history. These celebrations often include parades, fireworks, cultural performances, and other public events that bring communities together.

Please note that while these dates are widely recognized, specific traditions and observances can differ significantly between regions within the same country.