September 11 is officially designated as Patriot Day, not Patriots' Day. The two are distinct U.S. observances that commemorate different historical events. The similarity in their names is a common source of confusion.
Patriot Day, observed annually on September 11, is a national day of remembrance for the nearly 3,000 people killed in the terrorist attacks of September 11, 2001. Established by law in 2001, it is a day for flying the U.S. flag at half-staff and observing moments of silence. In contrast, Patriots' Day is a state holiday observed on the third Monday of April in Massachusetts, Maine, and Wisconsin. It commemorates the Battles of Lexington and Concord in 1775, which were the first armed conflicts of the American Revolutionary War.
In summary, the key distinction lies in the event being commemorated and the specific name. Patriot Day (singular) on September 11 honors the victims and heroes of the 2001 attacks, while Patriots' Day (plural possessive) in April celebrates the colonial patriots of the American Revolution. Using the correct term is essential for historical and civic accuracy.