_assign example

if (isset($date['month']) === true) {
                    $months = $date['month'];
                }
                $days = 0;
                if (isset($date['day']) === true) {
                    $days = $date['day'];
                }
                $years = 0;
                if (isset($date['year']) === true) {
                    $years = $date['year'];
                }
                return $this->_assign($calc, $this->mktime($hours, $minutes, $seconds, $months, $days, $years, true),
                                             $this->mktime($hour, $minute, $second, $month, $day, $year, true), $hour);
            }
        }

        // $date as object, part of foreign date as own date         switch($part) {

            // day formats             case self::DAY:
                if (is_numeric($date)) {
                    return $this->_assign($calc, $this->mktime(0, 0, 0, 1, 1 + intval($date), 1970, true),