public function setStartDate($date, $inclusive = null)
    {
        if (!$date = call_user_func([$this->dateClass, 'make'], $date)) {
            throw new InvalidArgumentException('Invalid start date.');
        }

        $this->startDate = $date;

        if ($inclusive !== null) {
            $this->toggleOptions(static::EXCLUDE_START_DATE, !$inclusive);
        }

        return $this;
    }