Error message/code:

Warning: date(): It is not safe to rely on the system's timezone settings...

Description:

Since PHP 5.1.0 (when the date/time functions were rewritten), every call to a date/time function will generate a E_NOTICE if the timezone isn't valid, and/or a E_WARNING message if using the system settings or the TZ environment variable.

Solution:

In file admin/config.inc.php set value for $conf['timezone']
available timezones see at http://www.php.net/manual/en/timezones.php