diff --git a/COPYRIGHT b/COPYRIGHT
new file mode 100644
index 0000000..b6f565d
--- /dev/null
+++ b/COPYRIGHT
@@ -0,0 +1,15 @@
+Copyright (C) 2015 The Islandora Foundation and contributors
+
+This program is free software; you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation; either version 2 of the License, or (at
+your option) any later version.
+
+This program is distributed in the hope that it will be useful, but
+WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
+or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
+for more details.
+
+You should have received a copy of the GNU General Public License
+along with this program as the file LICENSE.txt; if not, please see
+http://www.gnu.org/licenses/old-licenses/gpl-2.0.txt.
diff --git a/src/Plugin/Field/FieldFormatter/EDTFFormatter.php b/src/Plugin/Field/FieldFormatter/EDTFFormatter.php
index 19f7f45..31aacd5 100644
--- a/src/Plugin/Field/FieldFormatter/EDTFFormatter.php
+++ b/src/Plugin/Field/FieldFormatter/EDTFFormatter.php
@@ -27,7 +27,7 @@ class EDTFFormatter extends FormatterBase {
    *
    * @var array
    */
-  private $DELIMITERS = [
+  private const DELIMITERS = [
     'dash'   => '-',
     'stroke' => '/',
     'period' => '.',
@@ -276,7 +276,7 @@ protected function formatDate($edtf_text) {
       $formatted_date = "$month $day, $year";
     }
     else {
-      $formatted_date = implode($this->DELIMITERS[$settings['date_separator']], array_filter($parts_in_order));
+      $formatted_date = implode(self::DELIMITERS[$settings['date_separator']], array_filter($parts_in_order));
     }
 
     // Time.