diff --git a/doc/system/copyright.adoc b/doc/system/copyright.adoc
index 6f77e69..2349336 100644
--- a/doc/system/copyright.adoc
+++ b/doc/system/copyright.adoc
@@ -1,5 +1,5 @@
 ////
-Copyright 2018 Peter Dimov
+Copyright 2018-2021 Peter Dimov
 
 Distributed under the Boost Software License, Version 1.0.
 
@@ -14,6 +14,6 @@ http://www.boost.org/LICENSE_1_0.txt
 This documentation is
 
 * Copyright 2003-2017 Beman Dawes
-* Copyright 2018 Peter Dimov
+* Copyright 2018-2021 Peter Dimov
 
 and is distributed under the http://www.boost.org/LICENSE_1_0.txt[Boost Software License, Version 1.0].
diff --git a/doc/system/reference.adoc b/doc/system/reference.adoc
index 43e7988..a407b88 100644
--- a/doc/system/reference.adoc
+++ b/doc/system/reference.adoc
@@ -1,6 +1,6 @@
 ////
 Copyright 2003-2017 Beman Dawes
-Copyright 2018 Peter Dimov
+Copyright 2018-2021 Peter Dimov
 
 Distributed under the Boost Software License, Version 1.0.