public function setTimezone(\DateTimeZone $timezone = null)
    {
        if (!$timezone) {
            $timezone = $this->contactClient->getScheduleTimezone();
            if (!$timezone) {
                $timezone = $this->coreParametersHelper->getParameter(
                    'default_timezone'
                );
                $timezone = !empty($timezone) ? $timezone : date_default_timezone_get();
            }
            $timezone = new \DateTimeZone($timezone);
        }
        $this->timezone = $timezone;
        $this->now->setTimezone($timezone);

        return $this;
    }