i have an error in a website

Hi guy, i got an error in my website.
This one.

Warning: date() [function.date]: It is not safe to rely on the system's timezone settings. You are *required* to use the date.timezone setting 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 'America/Chicago' for '-6.0/no DST' instead in C:\xampp\htdocs\inc\functions.inc.php on line 31

Can you help me please. I would love you if you do... :thumbup: