The keyword phrase functions as an interrogative clause. It is not a single part of speech but a complete grammatical structure used to ask a question. This clause is composed of an interrogative adverb ("when"), a verb ("is"), a subject noun phrase ("Veterans Day"), and an adverbial phrase of time ("last year"). The entire construction's grammatical purpose is to solicit specific temporal information.
The central element and the grammatical subject of the clause is "Veterans Day," which is a proper noun phrase. A proper noun names a specific entity, in this case, a federal holiday. Within this phrase, the plural noun "Veterans" acts as a noun adjunct, modifying the noun "Day." The capitalization of both words signifies its status as a formal name. This proper noun phrase is the core topic around which the user's query is built.
For the purpose of creating an article, the main point should be anchored to the proper noun phrase "Veterans Day." While the full keyword is an interrogative clause, its semantic focus is this noun. The other components of the clause ("when," "last year") define the user's specific informational intent. Therefore, the article's structure should treat "Veterans Day" as the primary subject, with the content specifically addressing the historical date requested by the query.
