The error is quite enoying:

warning: 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 'UTC' for 'GMT/0.0/no DST' instead

But it is quite simple to correct. It is not a drupal problem, but a linux/apache. Just go to your php.ini, for example /etc/php.ini in CentOS and add this line:

date.timezone = Europe/London

reboot apache and the problem will have dissapeared.