Past - adjective, noun, adverb, or preposition ( Not an action verb) has to do with time
but "Sally and Larry walked past the boat." Past is used as an adverb. -ed past
'The woman passed by the man' - correct
'The boat sailed past us' - correct when used as an adverb
'The boat left half past nine' - correct-noun (time), 'He has a notorious past' - correct-noun or 'in the past' as a preposition.
Passed is the past participle of to pass. It is used to indicate movement.
Past is a noun, adverb, adjective, and preposition. It generally has something to do with time.