The subject of the inquiry, "Patriots' Day," functions as a proper noun. It is an official state holiday in Massachusetts, Maine, and Wisconsin, but it is not a federal holiday in the United States. Its status as a real, legally recognized holiday is therefore confined to specific jurisdictions rather than being nationally observed.
The holiday is observed on the third Monday in April. It commemorates the anniversary of the Battles of Lexington and Concord on April 19, 1775, which were the first armed conflicts of the American Revolutionary War. In Massachusetts and Maine, government offices, schools, and many private businesses close in observance. The day is marked by historical reenactments, parades, and most notably, the running of the Boston Marathon, which has been held on this day since 1897.
In conclusion, its legitimacy as a holiday is geographically dependent. For residents of the states where it is officially sanctioned, it is a significant public observance with legal standing. The common confusion about its status stems from its lack of federal recognition, which means it is not a holiday for the majority of the U.S. population or for federal employees outside the designated states.