Meanings
Usage patterns
過去を振り返るto look back on the past
It's nice to look back on the past once in a while.
〈人〉に過去があるsomeone has a (secret/troubled) past
He has a past he can't tell anyone about.
過去にさかのぼるto go back in time to the past
This story goes back ten years into the past.
〈動詞〉を過去形にするto put a verb into the past tense
Please put this verb into the past tense.
過去を消すto erase / wipe out one's past
He wanted to erase his past.
Expressions
暗い過去shadowy past; murky past; dark history 過去は過去the past is the past; let bygones be bygones