Depends on the sentence.
"The 1930s were the highlight of American culture." - subject, noun.
"Wow, your jeans are sooo 1930s." - predicate adjective, adjective
"I haven't partied that hard since the 1930s." - not sure, but a noun.
"How were the 1930s?" - predicate nominative, noun.
part of speech
Adjective
What part of speech is thaw
The part of speech for oscillate is verb.
An adjective is a part of speech.
The part of speech for this particular word is a noun.
part of speech
The part of speech for "answer" is a noun.
adverb
what part of speech is beneath
The part of speech for "unfamiliar" is an adjective.
The part of speech of "came" is a verb.
The part of speech for "twirl" is a verb.
The part of speech for "explicit" is an adjective.
The part of speech for "indefinite" is an adjective.
The part of speech for "lecturer" is a noun.
The part of speech for "breezy" is an adjective.