Urgent help!!! Error after upgrading to Vbulletin 4.2.2: “Warning: date() [function.date]: It is not safe…”

after updating my installation from Vbulletin version 4.2.1 to version 4.2.2 I can not access the forum. I can not access the control panel. When I try to access any page of the forum or admin panel, I find the following errors:

Warning: 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/London' for 'BST/1.0/DST' instead in ..../includes/functions.php on line 4912

Warning: strftime() [function.strftime]: 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/London’ for ‘BST/1.0/DST’ instead in …./includes/functions.php on line 5104

Warning: strftime() [function.strftime]: 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/London’ for ‘BST/1.0/DST’ instead in …./includes/functions.php on line 5104

Warning: 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/London’ for ‘BST/1.0/DST’ instead in …./includes/functions.php on line 5104

I am using HostGator’s web hosting. just add a line at your .htaccess file:
SetEnv TZ America/Indianapolis

You also can add one of the following code at the proper place of your PHP code:


or

at the beginning of config.php