Monday holidays. Martin Luther King, Jr. Birthday (third Monday in January), Washington's Birthday (third Monday in February), Patriot's Day (third Monday in April), Memorial Day (last Monday in May), Labor Day (first Monday in September) and Columbus Day (second Monday in October).
Other holidays. New Year's Day (January 1), Independence Day (July 4), Veterans' Day (November 11), Thanksgiving Day (fourth Thursday in November) and Christmas Day (December 25). March 17 and June 17 are holidays in Suffolk County.