The central term of the query, "Patriots' Day," functions as a proper noun. It is the subject of the inquiry, referring to a specific state holiday observed in Massachusetts and Maine.
The date of Patriots' Day is determined by state law, which designates the holiday to be observed on the third Monday in April. This floating date was established to ensure a three-day weekend. It commemorates the anniversary of the Battles of Lexington and Concord on April 19, 1775, which marked the beginning of the American Revolutionary War.
For the current year, 2024, Patriots' Day in Massachusetts is on Monday, April 15. In the upcoming year, 2025, it will be observed on Monday, April 21.