diff --git a/jsonschema-validation.xml b/jsonschema-validation.xml
index 21200f34..d8647bdb 100644
--- a/jsonschema-validation.xml
+++ b/jsonschema-validation.xml
@@ -543,13 +543,15 @@
 
             <section title="Defined Formats">
 
-                <section title="Dates and Times">
+                <section title="Dates, Times, and Duration">
                     <t>
                         These attributes apply to string instances.
                     </t>
                     <t>
                         Date and time format names are derived from
                         <xref target="RFC3339">RFC 3339, section 5.6</xref>.
+                        The duration format is from the ISO 8601 ABNF as given
+                        in Appendix A of RFC 3339.
                     </t>
                     <t>
                         Implementations supporting formats SHOULD implement support for
@@ -567,6 +569,10 @@
                                 A string instance is valid against this attribute if it is
                                 a valid representation according to the "full-time" production.
                             </t>
+                            <t hangText="duration:">
+                                A string instance is valid against this attribute if it is
+                                a valid representation according to the "duration" production.
+                            </t>
                         </list>
                     </t>
                     <t>