diff --git a/doc/src/sgml/ref/create_table.sgml b/doc/src/sgml/ref/create_table.sgml
index f19306e7760..4d47248fccf 100644
--- a/doc/src/sgml/ref/create_table.sgml
+++ b/doc/src/sgml/ref/create_table.sgml
@@ -888,6 +888,13 @@ WITH ( MODULUS <replaceable class="parameter">numeric_literal</replaceable>, REM
       match the data type of the column.
      </para>
 
+     <para>
+      Note, a string that returns a volatile result once cast to a data
+      type, like <literal>'now'::timestamptz</literal>, is evaluated at
+      table creation time, while <literal>now()::timestamptz</literal>
+      (without quotes) is evaluated at data insertion time.
+     </para>
+
      <para>
       The default expression will be used in any insert operation that
       does not specify a value for the column.  If there is no default