The keyword phrase is an interrogative sentence, with the central subject being "Patriots' Day," a proper noun. The question seeks to determine its classification as a "holiday," a common noun. The status of Patriots' Day is contingent on jurisdiction; it is officially recognized as a public holiday by specific state governments but is not a federal holiday in the United States.
Patriots' Day is an official state holiday in Massachusetts, Maine, and Wisconsin, observed on the third Monday in April. It commemorates the anniversary of the Battles of Lexington and Concord, the first military engagements of the American Revolutionary War, which took place on April 19, 1775. In these states, state, county, and municipal government offices and many public schools close. Connecticut also marks the day with official observances but does not recognize it as a legal public holiday where workers are given a paid day off.
Therefore, Patriots' Day remains a legally recognized holiday, but its observance is regional rather than national. Its most prominent public association is with the annual running of the Boston Marathon in Massachusetts. The distinction between its status as a state holiday versus a federal one is the primary reason for confusion regarding its observance across the country.