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 (Canada Day and Fiji Day), or other name. In the U.S. it is most commonly referred to as the 4th of July.
This is the day that celebrates the nation! It brings out the spirit of the nation and and develops a sense of national identity and heritage. Some countries celebrate more somberly while in many countries it is a day of celebration and still others celebrate it both ways.
The date is typically commemorative of the date a proclamation, declaration, end of a war, military occupation or foreign rule. It is commonly referred to as the birth of the nation, when it became it's own independent country. It is most often observed as a public or bank holiday where employees are off work and most businesses are closed.
Other related holidays: Republic Day, Victory Day, Liberation Day.