The phrase "11 sep 8pm est" functions as a phrasal unit, most commonly an adverbial phrase of time. It is not a single part of speech but a collection of words (numerals, an abbreviated proper noun, and an abbreviated noun phrase) that work together to modify a verb, adjective, or another adverb by specifying a precise point in time. Its grammatical role is fundamentally to answer the question "When?".
In a detailed analysis, the phrase's function is context-dependent. As an adverbial phrase, it modifies a verb, as in, "The broadcast will air 11 sep 8pm est." It can also function as a noun phrase when it acts as the subject or object of a sentence, such as, "11 sep 8pm est is the official start time." Furthermore, it can serve as an adjectival phrase (or phrasal adjective) when it modifies a noun, for example, "The 11 sep 8pm est deadline is approaching." The individual components"11" (cardinal number), "sep" (abbreviation of the proper noun September), "8pm" (a specific time), and "est" (abbreviation for the proper noun phrase Eastern Standard Time)combine to form a specific temporal designator whose classification is determined by its syntactic role within a larger sentence structure.
Ultimately, the practical interpretation is that this phrase operates as a singular unit of temporal information. While it can adopt different grammatical roles, its primary and most frequent function is adverbial. Understanding this allows for precise and correct placement within a sentence to convey a specific date and time without ambiguity. Its classification as an adverbial, noun, or adjectival phrase is less about its inherent nature and more about its relationship to the other words in a sentence.
