past vs pastness

past and pastness both are nouns.

Word	Noun	Adjective	Verb	Adverb
past	Yes	Yes	No	Yes
pastness	Yes	No	No	No

past (noun)	pastness (noun)
a verb tense that expresses actions or states in the past	the quality of being past
the time that has elapsed
a earlier period in someone's life (especially one that they have reason to keep secret)

past (adjective)	pastness (adjective)
earlier than the present time; no longer current
of a person who has held and relinquished a position or office

past (adverb)	pastness (adverb)
so as to pass a given point