php corbon date in a for loop in laravel 5.1

$date = new Carbon($request->posted_at);

    for($i=0;$i<$request->duration;$i++)
    {
        $newDate=$date->addMoth();
        $schedule = new LoanSchedual(['dueDate' => $newDate]);
        $loan->loanSchedules()->save($schedule);
    }

so that i get this
2016-10-18
2016-11-18
2016-12-18
2017-1-18
2016-10-18...etc

via Chebli Mohamed