The keyword phrase is an interrogative clause, a direct question seeking the specific date of a civic holiday. Patriots' Day is an official state holiday in Massachusetts and Maine, observed annually on the third Monday of April.
This holiday commemorates the anniversary of the Battles of Lexington and Concord, which occurred on April 19, 1775, marking the start of the American Revolutionary War. While originally celebrated on the fixed date of April 19, legislation enacted in Massachusetts in 1969 moved the official observance to the third Monday of the month. This change was implemented to create a three-day weekend. The day is also notable for hosting the Boston Marathon, which has been run on the holiday every year since 1897.
Consequently, the observance of the holiday occurs on a variable date each year, determined by its position as the third Monday in April rather than the fixed historical anniversary of the 19th. The inclusion of "Boston" in the query highlights the city's central role in the holiday's historical origins and its major contemporary civic traditions, particularly the marathon, which define the modern celebration.
