Constitution Day (Citizenship Day)
Calendars of different countries: US Holidays
Constitution Day or Citizenship Day is an American federal observance that recognizes the adoption of the United States Constitution and those who have become U.S. citizens. It is normally observed on September 17, the day in 1787 that delegates to the Constitutional Convention signed the document in Philadelphia.
When Constitution Day falls on a weekend or on another holiday, schools and other institutions observe the holiday on an adjacent weekday.
The law establishing the present holiday was created in 2004 with the passage of an amendment by Senator Robert Byrd to the Omnibus spending bill of 2004. Before this law was enacted, the holiday was known as "Citizenship Day". In addition to renaming the holiday "Constitution Day and Citizenship Day," the act mandates that all publicly funded educational institutions, and all federal agencies, provide educational programming on the United States Constitution on that day.
Source: wikipedia.org