The past is everything that has happened, whether we decide to happen based on our will or not, What is clear, that period will not turn back.
The past is also the reason we exist today, agree or not, our existence & circumstances today are the result of our past. That's what happened, yesterday is the past, now is the present, and tomorrow is the future. Period that never fused each other but stay connected to each other.
Vote back me @mizwar