Notice: Constant DATE_RFC7231 already defined in includes/bootstrap.inc on line 258 Drupal 7: Open /includes/bootstrap.inc Go to line number 258 Comment out the following line//define(‘DATE_RFC7231’, ‘D, d M Y H:i:s \G\M\T’); Then add following lineif (!defined(‘DATE_RFC7231’)) {define(‘DATE_RFC7231’, ‘D, d M Y H:i:s \G\M\T’);} Save and you are good to go 🙂