days vs years

days and years both are nouns.

Word	Noun	Adjective	Verb	Adverb
days	Yes	No	No	No
years	Yes	No	No	No

As nouns, days and years are synonyms defined as:

days (noun)	years (noun)
the time during which someone's life continues	a late time of life
	a prolonged period of time
	the time during which someone's life continues