مشكله في سكريبت opencart

السلام عليكم ورحمه الله

انا عندي مشكله تظهر في جميع الصفحات حتى لوحه التحكم وجود كود في اعلى الصفحات

Unknown: date() [function.date]: It is not safe to rely on the system's timezone settings. Please use the date.timezone setting, the TZ environment variable or the date_default_timezone_set() function. In case you used any of those methods and you are still getting this warning, you most likely misspelled the timezone identifier. We selected 'Europe/Helsinki' for 'EET/2.0/no DST' instead in /home/used/public_html/catalog/controller/common/footer.php on line 6