The keyword term is a noun phrase. Its primary grammatical function within a sentence is typically to act as an adverbial of time, specifying the exact temporal setting of an action or event. The core of the phrase is the proper noun "Patriots Day," which is modified by the temporal specifier "last year."
A detailed grammatical analysis reveals two main components. The head of the phrase is "Patriots Day," a proper noun that names a specific holiday. This noun is post-modified by the phrase "last year," which acts as a temporal adjective or adverbial. This modifier restricts the scope of the proper noun, distinguishing a specific past instance of the holiday from all other occurrences. The entire construction functions as a single, cohesive unit to pinpoint a particular point in time.
Understanding this structure is crucial for its application in writing. As a noun phrase functioning adverbially, it can be used to establish a timeframe, for example: "The Boston Marathon was held on Patriots Day last year." It can also function as the subject of a sentence ("Patriots Day last year was a memorable event.") or the object of a preposition ("This article is about Patriots Day last year."). The primary determination is that "Patriots Day" is the central noun, making the entire term a noun phrase that specifies time.
