[FATAL] Configuration variable date.timezone is not set, guessed timezone America/Chicago. Please set date.timezone="America/Chicago" in php.ini!

If you set that in your php.ini and are still getting that error, it’s likely getting thrown from you cronjob, which is calling the cli version of PHP. Make sure you add date.timezone="America/Chicago" to /etc/php5/apache2/php.ini and /etc/php5/cli/php.ini