diff --git a/draft-ietf-cbor-time-tag.html b/draft-ietf-cbor-time-tag.html
index 7a15947..c750c12 100644
--- a/draft-ietf-cbor-time-tag.html
+++ b/draft-ietf-cbor-time-tag.html
@@ -2064,36 +2064,47 @@ <h2 id="name-duration-format">
       <h2 id="name-period-format">
 <a href="#section-5" class="section-number selfRef">5. </a><a href="#name-period-format" class="section-name selfRef">Period Format</a>
       </h2>
-<p id="section-5-1">A period is a specific interval of time, specified as either two times
-giving the start and the end of that interval, or as one of these two
-plus a duration.<a href="#section-5-1" class="pilcrow">¶</a></p>
-<p id="section-5-2">They are given as an array of unwrapped time and duration elements,
-tagged with Tag 1003:<a href="#section-5-2" class="pilcrow">¶</a></p>
-<div class="lang-cddl sourcecode" id="section-5-3">
+<p id="section-5-1">A period is a specific interval of time, specified as either two
+extended times giving the start and the end of that interval, or as
+one of these two plus a duration.<a href="#section-5-1" class="pilcrow">¶</a></p>
+<p id="section-5-2">This is represented as an array of unwrapped time and duration elements,
+tagged with Tag 1003, one of:<a href="#section-5-2" class="pilcrow">¶</a></p>
+<ul class="normal">
+<li class="normal" id="section-5-3.1">
+          <p id="section-5-3.1.1">a start and end time, in which case the
+tag content is an array of two unwrapped extended time elements;<a href="#section-5-3.1.1" class="pilcrow">¶</a></p>
+</li>
+        <li class="normal" id="section-5-3.2">
+          <p id="section-5-3.2.1">a start time with duration or an end time with duration.
+The tag content is an array of 3 elements: the first two as
+above but either the start or end time <span class="bcp14">MUST</span> be set to null; the
+third one then is an unwrapped duration.<a href="#section-5-3.2.1" class="pilcrow">¶</a></p>
+</li>
+      </ul>
+<p id="section-5-4">A simple CDDL definition that does not capture all the constraints is:<a href="#section-5-4" class="pilcrow">¶</a></p>
+<div class="lang-cddl sourcecode" id="section-5-5">
 <pre>
-Period = #6.1003([
+simple-Period = #6.1003([
   start: ~Etime / null
   end: ~Etime / null
-  ? duration: ~Duration / null
+  ? duration: ~Duration
 ])
-</pre><a href="#section-5-3" class="pilcrow">¶</a>
+</pre><a href="#section-5-5" class="pilcrow">¶</a>
 </div>
-<p id="section-5-4">If the third array element is not given, the duration element is null.
-Exactly two out of the three elements must be non-null, this can be
-somewhat verbosely expressed in CDDL as:<a href="#section-5-4" class="pilcrow">¶</a></p>
-<div class="lang-cddl sourcecode" id="section-5-5">
+<p id="section-5-6">Exactly two out of the three elements must be present and non-null;
+this can be somewhat more verbosely expressed in CDDL as:<a href="#section-5-6" class="pilcrow">¶</a></p>
+<div class="lang-cddl sourcecode" id="section-5-7">
 <pre>
-clumsy-Period = #6.1003([
+Period = #6.1003([
   (start: ~Etime,
-   ((end: ~Etime,
-     ? duration: null) //
+   ((end: ~Etime) //
     (end: null,
      duration: ~Duration))) //
   (start: null,
    end: ~Etime,
    duration: ~Duration)
 ])
-</pre><a href="#section-5-5" class="pilcrow">¶</a>
+</pre><a href="#section-5-7" class="pilcrow">¶</a>
 </div>
 </section>
 </div>
diff --git a/draft-ietf-cbor-time-tag.txt b/draft-ietf-cbor-time-tag.txt
index 6787dfb..ef37ed7 100644
--- a/draft-ietf-cbor-time-tag.txt
+++ b/draft-ietf-cbor-time-tag.txt
@@ -119,9 +119,9 @@ Internet-Draft         CBOR tag for extended time           October 2023
    5.  Period Format . . . . . . . . . . . . . . . . . . . . . . . .  13
    6.  CDDL typenames  . . . . . . . . . . . . . . . . . . . . . . .  14
    7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  14
-     7.1.  CBOR tags . . . . . . . . . . . . . . . . . . . . . . . .  14
+     7.1.  CBOR tags . . . . . . . . . . . . . . . . . . . . . . . .  15
      7.2.  Timescale Registry  . . . . . . . . . . . . . . . . . . .  15
-     7.3.  Time Tag Map Key Registry . . . . . . . . . . . . . . . .  15
+     7.3.  Time Tag Map Key Registry . . . . . . . . . . . . . . . .  16
    8.  Security Considerations . . . . . . . . . . . . . . . . . . .  18
    9.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  18
      9.1.  Normative References  . . . . . . . . . . . . . . . . . .  18
@@ -714,14 +714,14 @@ Internet-Draft         CBOR tag for extended time           October 2023
 5.  Period Format
 
    A period is a specific interval of time, specified as either two
-   times giving the start and the end of that interval, or as one of
-   these two plus a duration.
-
-   They are given as an array of unwrapped time and duration elements,
-   tagged with Tag 1003:
-
+   extended times giving the start and the end of that interval, or as
+   one of these two plus a duration.
 
+   This is represented as an array of unwrapped time and duration
+   elements, tagged with Tag 1003, one of:
 
+   *  a start and end time, in which case the tag content is an array of
+      two unwrapped extended time elements;
 
 
 
@@ -730,20 +730,26 @@ Bormann, et al.           Expires 27 April 2024                [Page 13]
 Internet-Draft         CBOR tag for extended time           October 2023
 
 
-   Period = #6.1003([
+   *  a start time with duration or an end time with duration.  The tag
+      content is an array of 3 elements: the first two as above but
+      either the start or end time MUST be set to null; the third one
+      then is an unwrapped duration.
+
+   A simple CDDL definition that does not capture all the constraints
+   is:
+
+   simple-Period = #6.1003([
      start: ~Etime / null
      end: ~Etime / null
-     ? duration: ~Duration / null
+     ? duration: ~Duration
    ])
 
-   If the third array element is not given, the duration element is
-   null.  Exactly two out of the three elements must be non-null, this
-   can be somewhat verbosely expressed in CDDL as:
+   Exactly two out of the three elements must be present and non-null;
+   this can be somewhat more verbosely expressed in CDDL as:
 
-   clumsy-Period = #6.1003([
+   Period = #6.1003([
      (start: ~Etime,
-      ((end: ~Etime,
-        ? duration: null) //
+      ((end: ~Etime) //
        (end: null,
         duration: ~Duration))) //
      (start: null,
@@ -768,12 +774,6 @@ Internet-Draft         CBOR tag for extended time           October 2023
    // RFC Editor: please replace RFCthis with the RFC number of this
    // RFC, and remove this note.
 
-7.1.  CBOR tags
-
-   In the "CBOR Tags" registry [IANA.cbor-tags], IANA has allocated the
-   tags in Table 2 from what was at the time the FCFS space, with the
-   present document as the specification reference.
-
 
 
 
@@ -786,6 +786,12 @@ Bormann, et al.           Expires 27 April 2024                [Page 14]
 Internet-Draft         CBOR tag for extended time           October 2023
 
 
+7.1.  CBOR tags
+
+   In the "CBOR Tags" registry [IANA.cbor-tags], IANA has allocated the
+   tags in Table 2 from what was at the time the FCFS space, with the
+   present document as the specification reference.
+
               +======+===========+=========================+
               |  Tag | Data Item | Semantics               |
               +======+===========+=========================+
@@ -825,12 +831,6 @@ Internet-Draft         CBOR tag for extended time           October 2023
 
               Table 3: Initial Content of Timescale Registry
 
-7.3.  Time Tag Map Key Registry
-
-   This specification defines a new registry titled "Time Tag Map Keys"
-   in the "CBOR Tags" registry group [IANA.cbor-tags], with
-   "Specification Required" as the Registration Procedure (Section 4.6
-   of [BCP26]).
 
 
 
@@ -842,6 +842,13 @@ Bormann, et al.           Expires 27 April 2024                [Page 15]
 Internet-Draft         CBOR tag for extended time           October 2023
 
 
+7.3.  Time Tag Map Key Registry
+
+   This specification defines a new registry titled "Time Tag Map Keys"
+   in the "CBOR Tags" registry group [IANA.cbor-tags], with
+   "Specification Required" as the Registration Procedure (Section 4.6
+   of [BCP26]).
+
    The designated expert is requested to assign the key values with the
    shortest encodings (1+0 and 1+1 encoding) to registrations that are
    likely to enjoy wide use and can benefit from short encodings.
@@ -878,13 +885,6 @@ Internet-Draft         CBOR tag for extended time           October 2023
 
 
 
-
-
-
-
-
-
-
 
 
 
diff --git a/index.html b/index.html
index 2a90886..34e1684 100644
--- a/index.html
+++ b/index.html
@@ -69,7 +69,7 @@ <h2>Preview for branch <a href="iana-registries">iana-registries</a></h2>
       <tr>
         <td><a href="iana-registries/draft-ietf-cbor-time-tag.html" class="html draft-ietf-cbor-time-tag" title="Concise Binary Object Representation (CBOR) Tags for Time, Duration, and Period (HTML)">CBOR tag for extended time</a></td>
         <td><a href="iana-registries/draft-ietf-cbor-time-tag.txt" class="txt draft-ietf-cbor-time-tag" title="Concise Binary Object Representation (CBOR) Tags for Time, Duration, and Period (Text)">plain text</a></td>
-        <td>same as master</td>
+        <td><a href="https://author-tools.ietf.org/api/iddiff?url_1=https://cbor-wg.github.io/time-tag/draft-ietf-cbor-time-tag.txt&amp;url_2=https://cbor-wg.github.io/time-tag/iana-registries/draft-ietf-cbor-time-tag.txt" class="diff draft-ietf-cbor-time-tag">diff with master</a></td>
       </tr>
     </table>
     <h2>Preview for branch <a href="tf-artart-review-1">tf-artart-review-1</a></h2>