update copyright year
diff --git a/gradle/docs.gradle b/gradle/docs.gradle
index 530e0c0..d91243a 100644
--- a/gradle/docs.gradle
+++ b/gradle/docs.gradle
@@ -18,7 +18,7 @@
  */
 
 task doc(dependsOn: ['javadocAll', 'groovydocAll', 'docGDK', 'asciidocAll']) {
-    ext.footer = 'Copyright © 2003-2019 The Apache Software Foundation. All rights reserved.'
+    ext.footer = 'Copyright © 2003-2020 The Apache Software Foundation. All rights reserved.'
     ext.title = "Groovy ${groovyVersion}"
 }