In the context of the keyword phrase, "Patriots' Day" is a proper noun functioning as an adjective that modifies the implicit subject of "operations" or "schedule." "USPS" (United States Postal Service) is a proper noun serving as the subject. The phrase represents an inquiry into the operational status of the federal postal system in relation to a specific state-level holiday.
The United States Postal Service operates according to the schedule of federal holidays established by the U.S. Office of Personnel Management. Patriots' Day, which commemorates the opening battles of the American Revolutionary War, is an official state holiday only in Massachusetts and Maine, and a public school observance in Wisconsin. As it is not a federally recognized holiday, the USPS does not observe it. All Post Office locations maintain their regular hours, and mail collection and delivery services proceed as scheduled on Patriots' Day.
The practical application of this distinction is that individuals and businesses, even within states that formally observe Patriots' Day, can expect all USPS services to be fully operational. While local and state government offices, schools, and some private businesses in Massachusetts and Maine may be closed, the federal functions of the USPS are unaffected. Therefore, mail will be delivered and post offices will be open for business as on any other non-federal-holiday Monday.
