<?xml version='1.0' encoding='utf-8'?>
<rfc xmlns:xi="http://www.w3.org/2001/XInclude" version="3" submissionType="IETF" category="std" consensus="true" docName="draft-ietf-cbor-time-tag-12" number="9581" ipr="trust200902" sortRefs="true" symRefs="true" tocInclude="true" updates="" obsoletes="" xml:lang="en" prepTime="2024-08-16T12:44:46" indexInclude="true" scripts="Common,Greek,Latin" tocDepth="3">
  <link href="https://datatracker.ietf.org/doc/draft-ietf-cbor-time-tag-12" rel="prev"/>
  <link href="https://dx.doi.org/10.17487/rfc9581" rel="alternate"/>
  <link href="urn:issn:2070-1721" rel="alternate"/>
  <front>
    <title abbrev="CBOR Tag for Extended Time">Concise Binary Object Representation (CBOR) Tags for Time, Duration, and Period</title>
    <seriesInfo name="RFC" value="9581" stream="IETF"/>
    <author fullname="Carsten Bormann" initials="C." surname="Bormann">
      <organization showOnFrontPage="true">Universität Bremen TZI</organization>
      <address>
        <postal>
          <street>Postfach 330440</street>
          <city>Bremen</city>
          <code>D-28359</code>
          <country>Germany</country>
        </postal>
        <phone>+49-421-218-63921</phone>
        <email>cabo@tzi.org</email>
      </address>
    </author>
    <author fullname="Ben Gamari" initials="B." surname="Gamari">
      <organization showOnFrontPage="true">Well-Typed</organization>
      <address>
        <postal>
          <street>117 Middle Rd.</street>
          <city>Portsmouth</city>
          <region>NH</region>
          <code>03801</code>
          <country>United States of America</country>
        </postal>
        <email>ben@well-typed.com</email>
      </address>
    </author>
    <author fullname="Henk Birkholz" initials="H." surname="Birkholz">
      <organization abbrev="Fraunhofer SIT" showOnFrontPage="true">Fraunhofer Institute for Secure Information Technology</organization>
      <address>
        <postal>
          <street>Rheinstrasse 75</street>
          <city>Darmstadt</city>
          <code>64295</code>
          <country>Germany</country>
        </postal>
        <email>henk.birkholz@ietf.contact</email>
      </address>
    </author>
    <date month="08" year="2024"/>
    <area>art</area>
    <workgroup>cbor</workgroup>
    <keyword>Point in time</keyword>
    <keyword>Duration</keyword>
    <keyword>Period in time</keyword>
    <keyword>Clock accuracy</keyword>
    <keyword>Timescale</keyword>
    <keyword>TAI</keyword>
    <keyword>UTC</keyword>
    <keyword>NTP</keyword>
    <keyword>Network Time Protocol</keyword>
    <keyword>PTP</keyword>
    <keyword>Precision Time Protocol</keyword>
    <abstract pn="section-abstract">
      <t indent="0" pn="section-abstract-1">The Concise Binary Object Representation (CBOR, RFC 8949) is a data
format whose design goals include the possibility of extremely small
code size, fairly small message size, and extensibility without the
need for version negotiation.</t>
      <t indent="0" pn="section-abstract-2">In CBOR, one point of extensibility is the definition of CBOR tags.
RFC 8949 defines two tags for time: CBOR tag 0 (RFC 3339 time as a string) and tag
1 (POSIX time as int or float).  Since then, additional requirements have
become known.  The present document defines a CBOR tag for time that
allows a more elaborate representation of time, as well as related
CBOR tags for duration and time period.  This document is
intended as the reference document for the IANA registration of the
CBOR tags defined.</t>
    </abstract>
    <boilerplate>
      <section anchor="status-of-memo" numbered="false" removeInRFC="false" toc="exclude" pn="section-boilerplate.1">
        <name slugifiedName="name-status-of-this-memo">Status of This Memo</name>
        <t indent="0" pn="section-boilerplate.1-1">
            This is an Internet Standards Track document.
        </t>
        <t indent="0" pn="section-boilerplate.1-2">
            This document is a product of the Internet Engineering Task Force
            (IETF).  It represents the consensus of the IETF community.  It has
            received public review and has been approved for publication by
            the Internet Engineering Steering Group (IESG).  Further
            information on Internet Standards is available in Section 2 of 
            RFC 7841.
        </t>
        <t indent="0" pn="section-boilerplate.1-3">
            Information about the current status of this document, any
            errata, and how to provide feedback on it may be obtained at
            <eref target="https://www.rfc-editor.org/info/rfc9581" brackets="none"/>.
        </t>
      </section>
      <section anchor="copyright" numbered="false" removeInRFC="false" toc="exclude" pn="section-boilerplate.2">
        <name slugifiedName="name-copyright-notice">Copyright Notice</name>
        <t indent="0" pn="section-boilerplate.2-1">
            Copyright (c) 2024 IETF Trust and the persons identified as the
            document authors. All rights reserved.
        </t>
        <t indent="0" pn="section-boilerplate.2-2">
            This document is subject to BCP 78 and the IETF Trust's Legal
            Provisions Relating to IETF Documents
            (<eref target="https://trustee.ietf.org/license-info" brackets="none"/>) in effect on the date of
            publication of this document. Please review these documents
            carefully, as they describe your rights and restrictions with
            respect to this document. Code Components extracted from this
            document must include Revised BSD License text as described in
            Section 4.e of the Trust Legal Provisions and are provided without
            warranty as described in the Revised BSD License.
        </t>
      </section>
    </boilerplate>
    <toc>
      <section anchor="toc" numbered="false" removeInRFC="false" toc="exclude" pn="section-toc.1">
        <name slugifiedName="name-table-of-contents">Table of Contents</name>
        <ul bare="true" empty="true" indent="2" spacing="compact" pn="section-toc.1-1">
          <li pn="section-toc.1-1.1">
            <t indent="0" keepWithNext="true" pn="section-toc.1-1.1.1"><xref derivedContent="1" format="counter" sectionFormat="of" target="section-1"/>.  <xref derivedContent="" format="title" sectionFormat="of" target="name-introduction">Introduction</xref></t>
            <ul bare="true" empty="true" indent="2" spacing="compact" pn="section-toc.1-1.1.2">
              <li pn="section-toc.1-1.1.2.1">
                <t indent="0" keepWithNext="true" pn="section-toc.1-1.1.2.1.1"><xref derivedContent="1.1" format="counter" sectionFormat="of" target="section-1.1"/>.  <xref derivedContent="" format="title" sectionFormat="of" target="name-terminology">Terminology</xref></t>
              </li>
            </ul>
          </li>
          <li pn="section-toc.1-1.2">
            <t indent="0" keepWithNext="true" pn="section-toc.1-1.2.1"><xref derivedContent="2" format="counter" sectionFormat="of" target="section-2"/>.  <xref derivedContent="" format="title" sectionFormat="of" target="name-objectives">Objectives</xref></t>
          </li>
          <li pn="section-toc.1-1.3">
            <t indent="0" pn="section-toc.1-1.3.1"><xref derivedContent="3" format="counter" sectionFormat="of" target="section-3"/>.  <xref derivedContent="" format="title" sectionFormat="of" target="name-time-format">Time Format</xref></t>
            <ul bare="true" empty="true" indent="2" spacing="compact" pn="section-toc.1-1.3.2">
              <li pn="section-toc.1-1.3.2.1">
                <t indent="0" pn="section-toc.1-1.3.2.1.1"><xref derivedContent="3.1" format="counter" sectionFormat="of" target="section-3.1"/>.  <xref derivedContent="" format="title" sectionFormat="of" target="name-key-1">Key 1</xref></t>
              </li>
              <li pn="section-toc.1-1.3.2.2">
                <t indent="0" pn="section-toc.1-1.3.2.2.1"><xref derivedContent="3.2" format="counter" sectionFormat="of" target="section-3.2"/>.  <xref derivedContent="" format="title" sectionFormat="of" target="name-keys-4-and-5">Keys 4 and 5</xref></t>
              </li>
              <li pn="section-toc.1-1.3.2.3">
                <t indent="0" pn="section-toc.1-1.3.2.3.1"><xref derivedContent="3.3" format="counter" sectionFormat="of" target="section-3.3"/>.  <xref derivedContent="" format="title" sectionFormat="of" target="name-keys-3-6-9-12-15-and-18">Keys -3, -6, -9, -12, -15, and -18</xref></t>
              </li>
              <li pn="section-toc.1-1.3.2.4">
                <t indent="0" pn="section-toc.1-1.3.2.4.1"><xref derivedContent="3.4" format="counter" sectionFormat="of" target="section-3.4"/>.  <xref derivedContent="" format="title" sectionFormat="of" target="name-keys-1-13-and-13-timescale">Keys -1, -13, and 13: Timescale</xref></t>
              </li>
              <li pn="section-toc.1-1.3.2.5">
                <t indent="0" pn="section-toc.1-1.3.2.5.1"><xref derivedContent="3.5" format="counter" sectionFormat="of" target="section-3.5"/>.  <xref derivedContent="" format="title" sectionFormat="of" target="name-clock-quality">Clock Quality</xref></t>
                <ul bare="true" empty="true" indent="2" spacing="compact" pn="section-toc.1-1.3.2.5.2">
                  <li pn="section-toc.1-1.3.2.5.2.1">
                    <t indent="0" pn="section-toc.1-1.3.2.5.2.1.1"><xref derivedContent="3.5.1" format="counter" sectionFormat="of" target="section-3.5.1"/>.  <xref derivedContent="" format="title" sectionFormat="of" target="name-clockclass-key-2">ClockClass (Key -2)</xref></t>
                  </li>
                  <li pn="section-toc.1-1.3.2.5.2.2">
                    <t indent="0" pn="section-toc.1-1.3.2.5.2.2.1"><xref derivedContent="3.5.2" format="counter" sectionFormat="of" target="section-3.5.2"/>.  <xref derivedContent="" format="title" sectionFormat="of" target="name-clockaccuracy-key-4">ClockAccuracy (Key -4)</xref></t>
                  </li>
                  <li pn="section-toc.1-1.3.2.5.2.3">
                    <t indent="0" pn="section-toc.1-1.3.2.5.2.3.1"><xref derivedContent="3.5.3" format="counter" sectionFormat="of" target="section-3.5.3"/>.  <xref derivedContent="" format="title" sectionFormat="of" target="name-offsetscaledlogvariance-key">OffsetScaledLogVariance (Key -5)</xref></t>
                  </li>
                  <li pn="section-toc.1-1.3.2.5.2.4">
                    <t indent="0" pn="section-toc.1-1.3.2.5.2.4.1"><xref derivedContent="3.5.4" format="counter" sectionFormat="of" target="section-3.5.4"/>.  <xref derivedContent="" format="title" sectionFormat="of" target="name-uncertainty-key-7">Uncertainty (Key -7)</xref></t>
                  </li>
                  <li pn="section-toc.1-1.3.2.5.2.5">
                    <t indent="0" pn="section-toc.1-1.3.2.5.2.5.1"><xref derivedContent="3.5.5" format="counter" sectionFormat="of" target="section-3.5.5"/>.  <xref derivedContent="" format="title" sectionFormat="of" target="name-guarantee-key-8">Guarantee (Key -8)</xref></t>
                  </li>
                </ul>
              </li>
              <li pn="section-toc.1-1.3.2.6">
                <t indent="0" pn="section-toc.1-1.3.2.6.1"><xref derivedContent="3.6" format="counter" sectionFormat="of" target="section-3.6"/>.  <xref derivedContent="" format="title" sectionFormat="of" target="name-keys-10-10-time-zone-hint">Keys -10, 10: Time Zone Hint</xref></t>
              </li>
              <li pn="section-toc.1-1.3.2.7">
                <t indent="0" pn="section-toc.1-1.3.2.7.1"><xref derivedContent="3.7" format="counter" sectionFormat="of" target="section-3.7"/>.  <xref derivedContent="" format="title" sectionFormat="of" target="name-keys-11-11-ixdtf-suffix-inf">Keys -11, 11: IXDTF Suffix Information</xref></t>
              </li>
            </ul>
          </li>
          <li pn="section-toc.1-1.4">
            <t indent="0" pn="section-toc.1-1.4.1"><xref derivedContent="4" format="counter" sectionFormat="of" target="section-4"/>.  <xref derivedContent="" format="title" sectionFormat="of" target="name-duration-format">Duration Format</xref></t>
          </li>
          <li pn="section-toc.1-1.5">
            <t indent="0" pn="section-toc.1-1.5.1"><xref derivedContent="5" format="counter" sectionFormat="of" target="section-5"/>.  <xref derivedContent="" format="title" sectionFormat="of" target="name-period-format">Period Format</xref></t>
          </li>
          <li pn="section-toc.1-1.6">
            <t indent="0" pn="section-toc.1-1.6.1"><xref derivedContent="6" format="counter" sectionFormat="of" target="section-6"/>.  <xref derivedContent="" format="title" sectionFormat="of" target="name-cddl-type-names">CDDL Type Names</xref></t>
          </li>
          <li pn="section-toc.1-1.7">
            <t indent="0" pn="section-toc.1-1.7.1"><xref derivedContent="7" format="counter" sectionFormat="of" target="section-7"/>.  <xref derivedContent="" format="title" sectionFormat="of" target="name-iana-considerations">IANA Considerations</xref></t>
            <ul bare="true" empty="true" indent="2" spacing="compact" pn="section-toc.1-1.7.2">
              <li pn="section-toc.1-1.7.2.1">
                <t indent="0" pn="section-toc.1-1.7.2.1.1"><xref derivedContent="7.1" format="counter" sectionFormat="of" target="section-7.1"/>.  <xref derivedContent="" format="title" sectionFormat="of" target="name-cbor-tags">CBOR Tags</xref></t>
              </li>
              <li pn="section-toc.1-1.7.2.2">
                <t indent="0" pn="section-toc.1-1.7.2.2.1"><xref derivedContent="7.2" format="counter" sectionFormat="of" target="section-7.2"/>.  <xref derivedContent="" format="title" sectionFormat="of" target="name-timescales-registry">Timescales Registry</xref></t>
              </li>
              <li pn="section-toc.1-1.7.2.3">
                <t indent="0" pn="section-toc.1-1.7.2.3.1"><xref derivedContent="7.3" format="counter" sectionFormat="of" target="section-7.3"/>.  <xref derivedContent="" format="title" sectionFormat="of" target="name-time-tag-map-keys-registry">Time Tag Map Keys Registry</xref></t>
              </li>
            </ul>
          </li>
          <li pn="section-toc.1-1.8">
            <t indent="0" pn="section-toc.1-1.8.1"><xref derivedContent="8" format="counter" sectionFormat="of" target="section-8"/>.  <xref derivedContent="" format="title" sectionFormat="of" target="name-security-considerations">Security Considerations</xref></t>
          </li>
          <li pn="section-toc.1-1.9">
            <t indent="0" pn="section-toc.1-1.9.1"><xref derivedContent="9" format="counter" sectionFormat="of" target="section-9"/>.  <xref derivedContent="" format="title" sectionFormat="of" target="name-references">References</xref></t>
            <ul bare="true" empty="true" indent="2" spacing="compact" pn="section-toc.1-1.9.2">
              <li pn="section-toc.1-1.9.2.1">
                <t indent="0" pn="section-toc.1-1.9.2.1.1"><xref derivedContent="9.1" format="counter" sectionFormat="of" target="section-9.1"/>.  <xref derivedContent="" format="title" sectionFormat="of" target="name-normative-references">Normative References</xref></t>
              </li>
              <li pn="section-toc.1-1.9.2.2">
                <t indent="0" pn="section-toc.1-1.9.2.2.1"><xref derivedContent="9.2" format="counter" sectionFormat="of" target="section-9.2"/>.  <xref derivedContent="" format="title" sectionFormat="of" target="name-informative-references">Informative References</xref></t>
              </li>
            </ul>
          </li>
          <li pn="section-toc.1-1.10">
            <t indent="0" pn="section-toc.1-1.10.1"><xref derivedContent="Appendix A" format="default" sectionFormat="of" target="section-appendix.a"/>.  <xref derivedContent="" format="title" sectionFormat="of" target="name-collected-cddl">Collected CDDL</xref></t>
          </li>
          <li pn="section-toc.1-1.11">
            <t indent="0" pn="section-toc.1-1.11.1"><xref derivedContent="" format="none" sectionFormat="of" target="section-appendix.b"/><xref derivedContent="" format="title" sectionFormat="of" target="name-acknowledgements">Acknowledgements</xref></t>
          </li>
          <li pn="section-toc.1-1.12">
            <t indent="0" pn="section-toc.1-1.12.1"><xref derivedContent="" format="none" sectionFormat="of" target="section-appendix.c"/><xref derivedContent="" format="title" sectionFormat="of" target="name-authors-addresses">Authors' Addresses</xref></t>
          </li>
        </ul>
      </section>
    </toc>
  </front>
  <middle>
    <section anchor="intro" numbered="true" removeInRFC="false" toc="include" pn="section-1">
      <name slugifiedName="name-introduction">Introduction</name>
      <t indent="0" pn="section-1-1">The Concise Binary Object Representation (CBOR) <xref target="RFC8949" format="default" sectionFormat="of" derivedContent="RFC8949"/> provides
for the interchange of structured data without a requirement for a
pre-agreed schema.
RFC 8949 defines a basic set of data types, as well as a tagging
mechanism that enables extending the set of data types supported via
an IANA registry for CBOR tags (see <xref target="IANA.cbor-tags" format="default" sectionFormat="of" derivedContent="IANA.cbor-tags"/> and <xref section="9.2" sectionFormat="of" target="RFC8949" format="default" derivedLink="https://rfc-editor.org/rfc/rfc8949#section-9.2" derivedContent="RFC8949"/>).</t>
      <t indent="0" pn="section-1-2">RFC 8949 defines two tags for time: CBOR tag 0 (<xref target="RFC3339" format="default" sectionFormat="of" derivedContent="RFC3339"/> time as a string) and tag
1 (POSIX time as int or float).  Since then, additional requirements have
become known.  The present document defines a CBOR tag for time that
allows a more elaborate representation of time, as well as related
CBOR tags for durations and time periods.  This document is
intended as the reference document for the IANA registration of the
CBOR tags defined.</t>
      <section anchor="terms" numbered="true" removeInRFC="false" toc="include" pn="section-1.1">
        <name slugifiedName="name-terminology">Terminology</name>
        <t indent="0" pn="section-1.1-1">
    The key words "<bcp14>MUST</bcp14>", "<bcp14>MUST NOT</bcp14>",
    "<bcp14>REQUIRED</bcp14>", "<bcp14>SHALL</bcp14>", "<bcp14>SHALL NOT</bcp14>",
    "<bcp14>SHOULD</bcp14>", "<bcp14>SHOULD NOT</bcp14>",
    "<bcp14>RECOMMENDED</bcp14>", "<bcp14>NOT RECOMMENDED</bcp14>",
    "<bcp14>MAY</bcp14>", and "<bcp14>OPTIONAL</bcp14>" in this document are to be
    interpreted as described in BCP 14 <xref target="RFC2119" format="default" sectionFormat="of" derivedContent="RFC2119"/> <xref target="RFC8174" format="default" sectionFormat="of" derivedContent="RFC8174"/> when, and only when, they appear in all capitals, as
    shown here.
        </t>
        <t indent="0" pn="section-1.1-2">The term "byte" is used in its now customary sense as a synonym for
"octet".</t>
        <t indent="0" pn="section-1.1-3">Superscript notation denotes exponentiation.  For example, 2 to the
power of 64 is notated: 2<sup>64</sup>.  In the plain-text rendition
of this specification, superscript notation is not available and
exponentiation is therefore rendered by the surrogate notation seen
here in the plain-text rendition.</t>
        <t indent="0" pn="section-1.1-4">CBOR diagnostic notation is defined in <xref section="8" sectionFormat="of" target="RFC8949" format="default" derivedLink="https://rfc-editor.org/rfc/rfc8949#section-8" derivedContent="RFC8949"/> and
<xref section="G" sectionFormat="of" target="RFC8610" format="default" derivedLink="https://rfc-editor.org/rfc/rfc8610#appendix-G" derivedContent="RFC8610"/>.
A machine-processable model of the data structures defined in this
specification is provided throughout the text using the Concise Data
Definition Language (CDDL) <xref target="RFC8610" format="default" sectionFormat="of" derivedContent="RFC8610"/>; <xref target="collected-cddl" format="default" sectionFormat="of" derivedContent="Appendix A"/> provides the
collected model information.</t>
        <t indent="0" pn="section-1.1-5">Several time-related terms, such as UTC and International Atomic Time (TAI), are discussed in
<xref target="RFC9557" format="default" sectionFormat="of" derivedContent="RFC9557"/>, which may be a useful companion document beyond its direct
use in Sections <xref format="counter" target="tzh" sectionFormat="of" derivedContent="3.6"/> and <xref format="counter" target="suff" sectionFormat="of" derivedContent="3.7"/>.</t>
      </section>
    </section>
    <section anchor="objectives" numbered="true" removeInRFC="false" toc="include" pn="section-2">
      <name slugifiedName="name-objectives">Objectives</name>
      <t indent="0" pn="section-2-1">For the time tag,
the present specification addresses the following objectives that go
beyond the original tags 0 and 1 (defined in Sections <xref section="3.4.1" sectionFormat="bare" target="RFC8949" format="default" derivedLink="https://rfc-editor.org/rfc/rfc8949#section-3.4.1" derivedContent="RFC8949"/> and <xref section="3.4.2" sectionFormat="bare" target="RFC8949" format="default" derivedLink="https://rfc-editor.org/rfc/rfc8949#section-3.4.2" derivedContent="RFC8949"/> of <xref target="RFC8949" format="default" sectionFormat="of" derivedContent="RFC8949"/>):</t>
      <ul spacing="normal" bare="false" empty="false" indent="3" pn="section-2-2">
        <li pn="section-2-2.1">
          <t indent="0" pn="section-2-2.1.1">Additional resolution for epoch-based time (as in tag 1).  CBOR tag 1 only provides for representation of time as an integer and as up to a binary64 floating-point value <xref target="IEEE754" format="default" sectionFormat="of" derivedContent="IEEE754"/>, which limits the resolution to approximately
microseconds at the time of writing (progressively becoming
worse over time).</t>
        </li>
        <li pn="section-2-2.2">
          <t indent="0" pn="section-2-2.2.1">Indication of timescale.  Tags 0 and 1 are defined for UTC; however, some
interchanges are better performed on TAI.  Other timescales may be
registered once they become relevant (e.g., one of the proposed
successors to UTC that might no longer use leap seconds or a
scale based on smeared leap seconds).</t>
        </li>
      </ul>
      <t indent="0" pn="section-2-3">By incorporating a way to transport <xref target="RFC9557" format="default" sectionFormat="of" derivedContent="RFC9557"/> suffix information (see Sections <xref target="tzh" format="counter" sectionFormat="of" derivedContent="3.6"/> and
<xref target="suff" format="counter" sectionFormat="of" derivedContent="3.7"/>), additional indications of intents about the                                                                       
interpretation of the time given can be provided; in particular, for instances of
time that, at the time they are being described, are in the future.
Intents might include information about time zones, daylight saving
times, preferred calendar representations, etc.</t>
      <t indent="0" pn="section-2-4">Semantics not covered by this document can be added by registering
additional map keys for the map that is the content of the tag (see
<tt>etime-detailed</tt> in <xref target="tag-1001" format="default" sectionFormat="of" derivedContent="Figure 1"/>),
the specification for
which is referenced by the registry entry (see <xref target="time-format" format="default" sectionFormat="of" derivedContent="Section 3"/>).</t>
      <t indent="0" pn="section-2-5">For example, map keys could be registered for direct representations
of natural platform time formats.  Some platforms use epoch-based
time formats that require some computation to convert them into the
representations allowed by tag 1; these computations can also lose
precision and cause ambiguities.  (The present specification does
not take a position on whether tag 1 can be "fixed" to include,
e.g., Decimal or Bigfloat representations.  It does define how to
use these representations with the extended time format.)</t>
      <t indent="0" pn="section-2-6">Additional tags are defined for durations and periods.</t>
    </section>
    <section anchor="time-format" numbered="true" removeInRFC="false" toc="include" pn="section-3">
      <name slugifiedName="name-time-format">Time Format</name>
      <t indent="0" pn="section-3-1">An extended time is indicated by CBOR tag 1001, the content of which is a map data
item (CBOR major type 5).  The map may contain integer (major types 0
and 1) or text string (major type 3) keys, with the value type
determined by each specific key.
For negative integer keys and text string values of the key,
implementations <bcp14>MUST</bcp14> ignore key/value pairs they do not understand;
these keys are "elective", as the extended time as a whole is still
usable without the information they carry if an implementation elects not to implement them. Conversely, implementations <bcp14>MUST</bcp14> signal an error
when encountering key/value pairs that use unsigned integer keys they do not understand or implement (these
are either "base time" or "critical", see below).</t>
      <t indent="0" pn="section-3-2">The map <bcp14>MUST</bcp14> contain exactly one unsigned integer key that specifies
the "base time" and <bcp14>MAY</bcp14> also contain one or more negative integer or
text-string keys, which may encode supplementary information.</t>
      <t indent="0" pn="section-3-3">Supplementary information <bcp14>MAY</bcp14> also be provided by additional unsigned
integer keys that are explicitly defined to provide supplementary
information (we say these keys are defined to be "critical"); as these
are required to be understood, there can be no confusion with base
time keys.</t>
      <t indent="0" pn="section-3-4">Negative integer and text string keys always supply supplementary
information (they are "elective", and this will not be explicitly stated
below).</t>
      <t indent="0" pn="section-3-5">Supplementary information may include:</t>
      <ul spacing="normal" bare="false" empty="false" indent="3" pn="section-3-6">
        <li pn="section-3-6.1">
          <t indent="0" pn="section-3-6.1.1">a higher precision time offset to be added to the base time,</t>
        </li>
        <li pn="section-3-6.2">
          <t indent="0" pn="section-3-6.2.1">a reference timescale and epoch different from the default UTC and 1970-01-01, and</t>
        </li>
        <li pn="section-3-6.3">
          <t indent="0" pn="section-3-6.3.1">information about clock quality parameters, such as source,
accuracy, and uncertainty.</t>
        </li>
      </ul>
      <t indent="0" pn="section-3-7">Additional keys can be defined by registering them in the "Time Tag Map Keys"
registry (<xref target="map-key-registry" format="default" sectionFormat="of" derivedContent="Section 7.3"/>).
Registered keys may, for instance, add intent information such as time zone, daylight saving time,
and/or possibly positioning coordinates to express information that would indicate a local time.</t>
      <t indent="0" pn="section-3-8">This document does not define supplementary text keys.
A number of both unsigned and negative-integer keys are defined in
the following subsections.</t>
      <t indent="0" pn="section-3-9"><xref target="tag-1001" format="default" sectionFormat="of" derivedContent="Figure 1"/> provides a formal definition of tag 1001 in CDDL.</t>
      <figure anchor="tag-1001" align="left" suppress-title="false" pn="figure-1">
        <name slugifiedName="name-cddl-definition-of-tag-1001">CDDL Definition of Tag 1001</name>
        <sourcecode type="cddl" markers="false" pn="section-3-10.1">
Etime = #6.1001(etime-detailed)

etime-framework = {
  uint =&gt; any ; at least one base time
  * (nint/text) =&gt; any ; elective supplementary information
  * uint =&gt; any ; critical supplementary information
}

etime-detailed = ({
  $$ETIME-BASETIME
  ClockQuality-group
  * $$ETIME-ELECTIVE
  * $$ETIME-CRITICAL
  * ((nint/text) .feature "etime-elective-extension") =&gt; any
  * (uint .feature "etime-critical-extension") =&gt; any
}) .within etime-framework
</sourcecode>
      </figure>
      <section anchor="key-1" numbered="true" removeInRFC="false" toc="include" pn="section-3.1">
        <name slugifiedName="name-key-1">Key 1</name>
        <t indent="0" pn="section-3.1-1">Key 1 indicates a base time value that is exactly like the data item that would
be tagged by CBOR tag 1 (POSIX time <xref target="TIME_T" format="default" sectionFormat="of" derivedContent="TIME_T"/> as int or float).
As described above, the time value indicated by the value under this
key can be further
modified by other keys.</t>
        <sourcecode type="cddl" markers="false" pn="section-3.1-2">
$$ETIME-BASETIME //= (1: ~time)
</sourcecode>
      </section>
      <section anchor="keys-4-and-5" numbered="true" removeInRFC="false" toc="include" pn="section-3.2">
        <name slugifiedName="name-keys-4-and-5">Keys 4 and 5</name>
        <t indent="0" pn="section-3.2-1">Keys 4 and 5 indicate a base time value and are like key 1, except that the data item is an array as
defined for CBOR tag 4 or 5, respectively.
This can be used to include a Decimal or Bigfloat epoch-based float
<xref target="TIME_T" format="default" sectionFormat="of" derivedContent="TIME_T"/> in an extended time, e.g., to achieve higher resolution or to
avoid rounding errors.</t>
        <sourcecode type="cddl" markers="false" pn="section-3.2-2">
$$ETIME-BASETIME //= (4: ~decfrac)
$$ETIME-BASETIME //= (5: ~bigfloat)
</sourcecode>
      </section>
      <section anchor="keys-3-6-9-12-15-18" numbered="true" removeInRFC="false" toc="include" pn="section-3.3">
        <name slugifiedName="name-keys-3-6-9-12-15-and-18">Keys -3, -6, -9, -12, -15, and -18</name>
        <t indent="0" pn="section-3.3-1">The keys -3, -6, -9, -12, -15, and -18 indicate additional decimal fractions by
giving an unsigned integer (major type 0) and scaling this with the
scale factor 1e-3, 1e-6, 1e-9, 1e-12, 1e-15, and 1e-18, respectively
(see <xref target="decfract" format="default" sectionFormat="of" derivedContent="Table 1"/>).
Each extended time data item <bcp14>MUST NOT</bcp14> contain more than one
of these keys.
These additional fractions are added to a base time in seconds <xref target="SI-SECOND" format="default" sectionFormat="of" derivedContent="SI-SECOND"/>
indicated by key 1, which then <bcp14>MUST</bcp14> also be present and <bcp14>MUST</bcp14> have an
integer value.</t>
        <table anchor="decfract" align="center" pn="table-1">
          <name slugifiedName="name-keys-for-decimally-scaled-f">Keys for Decimally Scaled Fractions</name>
          <thead>
            <tr>
              <th align="left" colspan="1" rowspan="1">Key</th>
              <th align="left" colspan="1" rowspan="1">Meaning</th>
              <th align="left" colspan="1" rowspan="1">Example Usage</th>
            </tr>
          </thead>
          <tbody>
            <tr>
              <td align="left" colspan="1" rowspan="1">-3</td>
              <td align="left" colspan="1" rowspan="1">milliseconds</td>
              <td align="left" colspan="1" rowspan="1">Java time</td>
            </tr>
            <tr>
              <td align="left" colspan="1" rowspan="1">-6</td>
              <td align="left" colspan="1" rowspan="1">microseconds</td>
              <td align="left" colspan="1" rowspan="1">(old) UNIX time</td>
            </tr>
            <tr>
              <td align="left" colspan="1" rowspan="1">-9</td>
              <td align="left" colspan="1" rowspan="1">nanoseconds</td>
              <td align="left" colspan="1" rowspan="1">(new) UNIX time</td>
            </tr>
            <tr>
              <td align="left" colspan="1" rowspan="1">-12</td>
              <td align="left" colspan="1" rowspan="1">picoseconds</td>
              <td align="left" colspan="1" rowspan="1">Haskell time</td>
            </tr>
            <tr>
              <td align="left" colspan="1" rowspan="1">-15</td>
              <td align="left" colspan="1" rowspan="1">femtoseconds</td>
              <td align="left" colspan="1" rowspan="1">(future)</td>
            </tr>
            <tr>
              <td align="left" colspan="1" rowspan="1">-18</td>
              <td align="left" colspan="1" rowspan="1">attoseconds</td>
              <td align="left" colspan="1" rowspan="1">(future)</td>
            </tr>
          </tbody>
        </table>
        <sourcecode type="cddl" markers="false" pn="section-3.3-3">
$$ETIME-ELECTIVE //= (-3: uint)
$$ETIME-ELECTIVE //= (-6: uint)
$$ETIME-ELECTIVE //= (-9: uint)
$$ETIME-ELECTIVE //= (-12: uint)
$$ETIME-ELECTIVE //= (-15: uint)
$$ETIME-ELECTIVE //= (-18: uint)
</sourcecode>
        <t indent="0" pn="section-3.3-4">Note that these keys have been provided to facilitate representing
pairs of the form second/decimal fraction of a second, as found for
instance in C <tt>timespec</tt> (Section 7.27.1 of <xref target="C" format="default" sectionFormat="of" derivedContent="C"/>).
When ingesting a timestamp with one of these keys into a type provided
by the target platform, care has to be taken to meet its invariants.
For example, for C <tt>timespec</tt>, the fractional part <tt>tv_nsec</tt> needs to be
between 0 inclusive and 10<sup>9</sup> exclusive, which can be
achieved by also adjusting the base time appropriately.</t>
      </section>
      <section anchor="key-timescale" numbered="true" removeInRFC="false" toc="include" pn="section-3.4">
        <name slugifiedName="name-keys-1-13-and-13-timescale">Keys -1, -13, and 13: Timescale</name>
        <t indent="0" pn="section-3.4-1">Keys -1, -13, and 13 are used to indicate a timescale, where key 13 is critical. Keys -1 and -13 have identical semantics (both are assigned because
 key -1 was chosen first and then, when key 13 was added, it appeared desirable to have a
 negative equivalent).
 Each extended time data item <bcp14>MUST NOT</bcp14>
	contain more than one of these keys.</t>
        <t indent="0" pn="section-3.4-2">The value 0 indicates UTC,
with the POSIX epoch <xref target="TIME_T" format="default" sectionFormat="of" derivedContent="TIME_T"/>; the value 1 indicates TAI, with the
Precision Time Protocol (PTP) epoch (1 January 1970 00:00:00 TAI, see
<xref target="IEEE1588-2019" format="default" sectionFormat="of" derivedContent="IEEE1588-2019"/> or <xref target="IEEE1588-2008" format="default" sectionFormat="of" derivedContent="IEEE1588-2008"/>).</t>
        <sourcecode type="cddl" markers="false" pn="section-3.4-3">
$$ETIME-ELECTIVE //= (-1 =&gt; $ETIME-TIMESCALE)
$$ETIME-ELECTIVE //= (-13 =&gt; $ETIME-TIMESCALE)
$$ETIME-CRITICAL //= (13 =&gt; $ETIME-TIMESCALE)

$ETIME-TIMESCALE /= &amp;(etime-utc: 0)
$ETIME-TIMESCALE /= &amp;(etime-tai: 1)
</sourcecode>
        <t indent="0" pn="section-3.4-4">If none of the keys are present, the default timescale value 0 is implied.</t>
        <t indent="0" pn="section-3.4-5">Timescale values <bcp14>MUST</bcp14> be unsigned integers or text strings; text strings are
provided for experimentation and <bcp14>MUST NOT</bcp14> be used between parties
that are not both part of the experiment.
Additional unsigned integer values can be registered in the "Timescales" registry
(<xref target="timescale-registry" format="default" sectionFormat="of" derivedContent="Section 7.2"/>).
(Note that there should be no timescales "GPS" or "NTP" <xref target="RFC5905" format="default" sectionFormat="of" derivedContent="RFC5905"/> -- instead,
the time should be converted to TAI or UTC using a single addition or subtraction.)</t>
        <figure anchor="offset" align="left" suppress-title="false" pn="figure-2">
          <name slugifiedName="name-converting-common-offset-ti">Converting Common Offset Timescales</name>
          <artset pn="section-3.4-6.1">
            <artwork type="svg" align="left" pn="section-3.4-6.1.1"><svg xmlns:xlink="http://www.w3.org/1999/xlink" xmlns="http://www.w3.org/2000/svg" height="6.009ex" role="img" viewBox="0 -791.3 43055.4 2587.3" width="100ex">
                <defs>
                  <path d="M283 438l-10 -38h-70l-78 -320c-1 -3 -2 -8 -2 -11c0 -6 3 -12 16 -12c0 0 23 2 60 52l13 -11c-24 -31 -74 -107 -133 -107c-31 0 -39 25 -39 52c0 13 2 26 5 37l81 320h-77l5 29c75 14 136 51 177 138h13l-31 -129h70Z" id="E1-STIXWEBNORMALI-1D461-gensym001" stroke-width="1"/>
                  <path d="M444 428l-89 -348c-1 -4 -1 -6 -1 -9c0 -8 4 -14 14 -14c21 0 40 26 57 46l5 6l13 -11c-23 -33 -74 -107 -132 -107c-29 0 -40 19 -40 52c0 9 1 25 4 37l26 95h-1c-7 -5 -97 -126 -137 -156c-23 -17 -49 -28 -72 -28c-47 0 -61 36 -61 74c0 21 3 40 8 59l59 231 c4 15 6 21 6 25c0 12 -11 23 -33 23c-7 0 -19 -1 -26 -3l-3 15l157 26l-84 -326c-2 -9 -3 -16 -3 -24c0 -21 8 -34 26 -34c25 0 65 31 100 77c43 57 89 146 109 219l21 75h77Z" id="E1-STIXWEBNORMALI-1D462-gensym001" stroke-width="1"/>
                  <path d="M363 111l12 -13c-51 -60 -113 -109 -198 -109c-97 0 -137 78 -137 155c0 140 121 297 263 297c50 0 97 -27 97 -76c0 -38 -16 -70 -54 -70c-26 0 -38 21 -38 38c0 24 29 36 29 58c0 12 -10 21 -34 21c-119 0 -176 -179 -176 -259c0 -87 49 -109 94 -109 c61 0 107 33 142 67Z" id="E1-STIXWEBNORMALI-1D450-gensym001" stroke-width="1"/>
                  <path d="M637 320h-589v66h589v-66zM637 120h-589v66h589v-66Z" id="E1-STIXWEBMAIN-3D-gensym001" stroke-width="1"/>
                  <path d="M467 96l-5 -6c-28 -34 -76 -98 -128 -98c-32 0 -41 23 -41 46c0 13 4 29 7 40l57 221c2 8 7 28 7 42c0 19 -6 38 -24 38c-38 0 -101 -86 -132 -133c-36 -54 -62 -101 -68 -122l-33 -124h-77l95 374c0 18 -3 32 -30 32c-10 0 -21 -2 -28 -3l-2 15l159 23l-51 -189h3 c5 0 54 70 56 73c40 50 100 116 160 116c44 0 56 -29 56 -62c0 -25 -6 -50 -11 -70l-59 -231c-1 -2 -1 -5 -1 -10c1 -6 4 -14 15 -14c24 0 48 36 62 53Z" id="E1-STIXWEBNORMALI-1D45B-gensym001" stroke-width="1"/>
                  <path d="M253 370l14 13c39 37 78 58 113 58c61 0 94 -54 94 -155c0 -129 -110 -298 -254 -298c-24 0 -42 4 -61 19l-24 -100c-3 -13 -5 -24 -5 -35c0 -22 11 -43 61 -43h16l-3 -12h-234l3 12c62 3 69 33 81 79l117 464c0 19 -1 33 -31 33c-8 0 -20 -2 -28 -4l-2 16l158 24 l-18 -69zM214 238l-46 -200c14 -16 34 -21 46 -21c101 0 176 173 176 285c0 63 -28 83 -51 83c-53 0 -105 -61 -125 -147Z" id="E1-STIXWEBNORMALI-1D45D-gensym001" stroke-width="1"/>
                  <path d="M621 220h-557v66h557v-66Z" id="E1-STIXWEBMAIN-2212-gensym001" stroke-width="1"/>
                  <path d="M474 137l-54 -137h-391v12l178 189c94 99 130 175 130 260c0 91 -54 141 -139 141c-72 0 -107 -32 -147 -130l-21 5c21 117 85 199 208 199c113 0 185 -77 185 -176c0 -79 -39 -154 -128 -248l-165 -176h234c42 0 63 11 96 67Z" id="E1-STIXWEBMAIN-32-gensym001" stroke-width="1"/>
                  <path d="M476 330c0 -172 -63 -344 -226 -344c-171 0 -226 186 -226 350c0 177 69 340 230 340c131 0 222 -141 222 -346zM380 325c0 208 -44 325 -132 325c-83 0 -128 -118 -128 -321s44 -317 130 -317c85 0 130 115 130 313Z" id="E1-STIXWEBMAIN-30-gensym001" stroke-width="1"/>
                  <path d="M445 155c0 -103 -77 -169 -197 -169c-113 0 -192 69 -192 163c0 69 23 108 130 183c-103 85 -124 123 -124 188c0 96 83 156 194 156c99 0 168 -65 168 -143c0 -75 -35 -109 -134 -162c123 -82 155 -136 155 -216zM355 533c0 69 -41 115 -109 115 c-67 0 -110 -37 -110 -99s37 -108 125 -160c68 40 94 82 94 144zM271 272l-59 40c-59 -48 -80 -89 -80 -154c0 -92 51 -144 127 -144c65 0 110 45 110 110c0 62 -30 102 -98 148Z" id="E1-STIXWEBMAIN-38-gensym001" stroke-width="1"/>
                  <path d="M59 -22l-3 20c152 27 264 132 304 296c-43 -42 -91 -57 -150 -57c-108 0 -180 81 -180 203c0 135 89 236 208 236c64 0 118 -28 157 -76c40 -50 64 -122 64 -206c0 -115 -40 -224 -120 -297c-85 -77 -150 -101 -280 -119zM362 355v39c0 168 -45 254 -132 254 c-30 0 -56 -12 -73 -34c-20 -27 -35 -86 -35 -140c0 -119 48 -194 123 -194c44 0 117 22 117 75Z" id="E1-STIXWEBMAIN-39-gensym001" stroke-width="1"/>
                  <path d="M472 428l-91 -345s-1 -2 -1 -11c0 -11 6 -17 14 -17c10 0 25 2 64 54l12 -12c-31 -47 -85 -107 -133 -107c-33 0 -42 23 -42 55c0 13 6 34 11 50h-4c-72 -92 -134 -105 -173 -105c-63 0 -89 55 -89 119c0 132 132 332 276 332c43 0 64 -24 66 -46h1l9 33h80zM367 341 c0 41 -12 71 -50 71c-68 0 -128 -87 -162 -171c-18 -45 -28 -89 -28 -124c0 -53 31 -66 58 -66c69 0 139 95 167 190c8 26 15 66 15 100Z" id="E1-STIXWEBNORMALI-1D44E-gensym001" stroke-width="1"/>
                  <path d="M257 566c0 -26 -22 -46 -48 -46c-29 0 -48 20 -48 46c0 25 19 50 48 50c26 0 48 -25 48 -50zM227 441l-92 -364c-1 -6 -1 -10 -1 -14c0 -7 6 -10 13 -10c22 0 28 12 64 51l13 -10c-35 -45 -85 -105 -134 -105c-28 0 -40 19 -40 46c0 12 0 31 79 338c1 2 2 9 2 12 c0 17 -8 22 -31 22c-9 0 -21 -2 -28 -4l-3 16Z" id="E1-STIXWEBNORMALI-1D456-gensym001" stroke-width="1"/>
                  <path d="M492 413l-13 -45h-81c13 -15 17 -28 17 -50c0 -75 -53 -137 -141 -148c-59 -8 -88 -33 -88 -58c0 -63 233 -23 233 -148c0 -71 -66 -151 -215 -151c-134 0 -184 57 -184 115s55 88 117 108c-17 11 -24 30 -24 47c0 38 37 87 85 87v4c-67 15 -94 62 -94 109 c0 79 68 158 174 158c42 0 73 -13 88 -28h126zM336 349c0 37 -10 62 -54 62c-54 0 -98 -71 -98 -139c0 -46 12 -81 56 -81c71 0 96 102 96 158zM349 -69c0 78 -132 73 -192 95c-8 -5 -18 -10 -26 -16c-26 -19 -48 -45 -48 -72c0 -47 44 -97 139 -97c91 0 127 46 127 90Z" id="E1-STIXWEBNORMALI-1D454-gensym001" stroke-width="1"/>
                  <path d="M390 441l-24 -146h-15c0 64 -36 120 -92 120c-25 0 -51 -17 -51 -58c0 -55 134 -147 134 -242c0 -62 -48 -125 -135 -125c-34 0 -98 20 -110 20c-9 0 -18 -4 -30 -21h-17l25 156h16c0 -63 41 -130 104 -130c59 0 73 50 73 89c0 82 -130 132 -130 230c0 79 59 107 114 107 c43 0 63 -20 92 -20c11 0 22 10 30 20h16Z" id="E1-STIXWEBNORMALI-1D460-gensym001" stroke-width="1"/>
                  <path d="M636 220h-261v-261h-66v261h-261v66h261v261h66v-261h261v-66Z" id="E1-STIXWEBMAIN-2B-gensym001" stroke-width="1"/>
                  <path d="M61 510l-16 4c29 95 92 162 196 162c93 0 156 -55 156 -137c0 -48 -26 -98 -93 -138c44 -19 62 -31 83 -53c28 -31 44 -77 44 -129c0 -53 -17 -102 -46 -140c-48 -64 -143 -93 -232 -93c-73 0 -112 21 -112 57c0 21 18 36 41 36c17 0 33 -6 61 -26c37 -26 58 -31 86 -31 c74 0 130 68 130 153c0 76 -35 125 -104 145c-22 7 -45 10 -102 10v14c38 13 64 24 84 36c49 28 81 73 81 134c0 68 -42 102 -108 102c-62 0 -108 -32 -149 -106Z" id="E1-STIXWEBMAIN-33-gensym001" stroke-width="1"/>
                  <path d="M394 0h-276v15c74 4 95 25 95 80v449c0 34 -9 49 -30 49c-10 0 -27 -5 -45 -12l-27 -10v14l179 91l9 -3v-597c0 -43 20 -61 95 -61v-15Z" id="E1-STIXWEBMAIN-31-gensym001" stroke-width="1"/>
                  <path d="M438 681l-36 -85c-3 -7 -11 -13 -27 -13h-194l-40 -85c143 -27 193 -49 250 -128c26 -36 35 -74 35 -127c0 -96 -30 -158 -98 -208c-47 -34 -102 -49 -170 -49c-75 0 -127 24 -127 62c0 25 17 38 45 38c23 0 42 -5 74 -31c28 -23 51 -32 71 -32c70 0 135 83 135 169 c0 64 -22 114 -67 150c-47 38 -117 70 -213 70c-9 0 -12 2 -12 8c0 2 1 5 1 5l109 237h207c23 0 32 5 48 26Z" id="E1-STIXWEBMAIN-35-gensym001" stroke-width="1"/>
                  <path d="M446 684l2 -16c-157 -26 -269 -134 -296 -285c49 38 83 45 127 45c117 0 189 -80 189 -209c0 -64 -18 -120 -51 -160c-37 -46 -93 -73 -159 -73c-79 0 -142 37 -177 101c-28 51 -47 122 -47 192c0 108 38 203 109 276c86 90 165 114 303 129zM378 188 c0 128 -42 194 -135 194c-57 0 -116 -24 -116 -116c0 -152 48 -252 142 -252c72 0 109 72 109 174Z" id="E1-STIXWEBMAIN-36-gensym001" stroke-width="1"/>
                  <path d="M473 167h-103v-167h-78v167h-280v64l314 445h44v-445h103v-64zM292 231v343l-240 -343h240Z" id="E1-STIXWEBMAIN-34-gensym001" stroke-width="1"/>
                </defs>
                <g fill="black" stroke="currentColor" stroke-width="0" transform="matrix(1 0 0 -1 0 0)">
                  <g transform="translate(16540,0)">
                    <use xlink:href="#E1-STIXWEBNORMALI-1D461-gensym001" x="0" y="0"/>
                    <g transform="translate(313,-150)">
                      <use xlink:href="#E1-STIXWEBNORMALI-1D462-gensym001" transform="scale(0.707)" x="0" y="0"/>
                      <use xlink:href="#E1-STIXWEBNORMALI-1D461-gensym001" transform="scale(0.707)" x="474" y="0"/>
                      <use xlink:href="#E1-STIXWEBNORMALI-1D450-gensym001" transform="scale(0.707)" x="788" y="0"/>
                    </g>
                    <use xlink:href="#E1-STIXWEBMAIN-3D-gensym001" x="1542" y="0"/>
                    <g transform="translate(2505,0)">
                      <use xlink:href="#E1-STIXWEBNORMALI-1D461-gensym001" x="0" y="0"/>
                      <g transform="translate(313,-150)">
                        <use xlink:href="#E1-STIXWEBNORMALI-1D45B-gensym001" transform="scale(0.707)" x="0" y="0"/>
                        <use xlink:href="#E1-STIXWEBNORMALI-1D461-gensym001" transform="scale(0.707)" x="497" y="0"/>
                        <use xlink:href="#E1-STIXWEBNORMALI-1D45D-gensym001" transform="scale(0.707)" x="810" y="0"/>
                      </g>
                    </g>
                    <use xlink:href="#E1-STIXWEBMAIN-2212-gensym001" x="4060" y="0"/>
                    <g transform="translate(4968,0)">
                      <use xlink:href="#E1-STIXWEBMAIN-32-gensym001"/>
                      <use xlink:href="#E1-STIXWEBMAIN-32-gensym001" x="500" y="0"/>
                      <use xlink:href="#E1-STIXWEBMAIN-30-gensym001" x="1001" y="0"/>
                      <use xlink:href="#E1-STIXWEBMAIN-38-gensym001" x="1501" y="0"/>
                      <use xlink:href="#E1-STIXWEBMAIN-39-gensym001" x="2002" y="0"/>
                      <use xlink:href="#E1-STIXWEBMAIN-38-gensym001" x="2502" y="0"/>
                      <use xlink:href="#E1-STIXWEBMAIN-38-gensym001" x="3003" y="0"/>
                      <use xlink:href="#E1-STIXWEBMAIN-38-gensym001" x="3503" y="0"/>
                      <use xlink:href="#E1-STIXWEBMAIN-30-gensym001" x="4004" y="0"/>
                      <use xlink:href="#E1-STIXWEBMAIN-30-gensym001" x="4504" y="0"/>
                    </g>
                  </g>
                  <g transform="translate(16774,-1400)">
                    <use xlink:href="#E1-STIXWEBNORMALI-1D461-gensym001" x="0" y="0"/>
                    <g transform="translate(313,-150)">
                      <use xlink:href="#E1-STIXWEBNORMALI-1D461-gensym001" transform="scale(0.707)" x="0" y="0"/>
                      <use xlink:href="#E1-STIXWEBNORMALI-1D44E-gensym001" transform="scale(0.707)" x="313" y="0"/>
                      <use xlink:href="#E1-STIXWEBNORMALI-1D456-gensym001" transform="scale(0.707)" x="816" y="0"/>
                    </g>
                    <use xlink:href="#E1-STIXWEBMAIN-3D-gensym001" x="1488" y="0"/>
                    <g transform="translate(2451,0)">
                      <use xlink:href="#E1-STIXWEBNORMALI-1D461-gensym001" x="0" y="0"/>
                      <g transform="translate(313,-150)">
                        <use xlink:href="#E1-STIXWEBNORMALI-1D454-gensym001" transform="scale(0.707)" x="0" y="0"/>
                        <use xlink:href="#E1-STIXWEBNORMALI-1D45D-gensym001" transform="scale(0.707)" x="492" y="0"/>
                        <use xlink:href="#E1-STIXWEBNORMALI-1D460-gensym001" transform="scale(0.707)" x="982" y="0"/>
                      </g>
                    </g>
                    <use xlink:href="#E1-STIXWEBMAIN-2B-gensym001" x="4093" y="0"/>
                    <g transform="translate(5001,0)">
                      <use xlink:href="#E1-STIXWEBMAIN-33-gensym001"/>
                      <use xlink:href="#E1-STIXWEBMAIN-31-gensym001" x="500" y="0"/>
                      <use xlink:href="#E1-STIXWEBMAIN-35-gensym001" x="1001" y="0"/>
                      <use xlink:href="#E1-STIXWEBMAIN-39-gensym001" x="1501" y="0"/>
                      <use xlink:href="#E1-STIXWEBMAIN-36-gensym001" x="2002" y="0"/>
                      <use xlink:href="#E1-STIXWEBMAIN-34-gensym001" x="2502" y="0"/>
                      <use xlink:href="#E1-STIXWEBMAIN-38-gensym001" x="3003" y="0"/>
                      <use xlink:href="#E1-STIXWEBMAIN-31-gensym001" x="3503" y="0"/>
                      <use xlink:href="#E1-STIXWEBMAIN-39-gensym001" x="4004" y="0"/>
                    </g>
                  </g>
                </g>
              </svg>
            </artwork>
            <artwork type="ascii-art" align="left" pn="section-3.4-6.1.2">t    = t    - 2208988800
 utc    ntp

t    = t    + 315964819
 tai    gps
</artwork>
          </artset>
        </figure>
        <aside pn="section-3.4-7">
          <t indent="0" pn="section-3.4-7.1">Editor's note:
This initial set of timescales was deliberately chosen to be frugal, as
the specification of the tag provides an extension point where
additional timescales can be registered at any time.
Registrations are clearly needed for earth-referenced timescales (such
as UT1 and TT), as well as possibly for specific realizations of
abstract timescales (such as TAI(USNO), the specific realization obtained at the United States Naval Observatory, which is more accurate as a
constant offset basis for GPS times).
While the registration process itself is trivial, these registrations
need to be made based on a solid specification of their actual
definition.</t>
        </aside>
      </section>
      <section anchor="clock-quality" numbered="true" removeInRFC="false" toc="include" pn="section-3.5">
        <name slugifiedName="name-clock-quality">Clock Quality</name>
        <t indent="0" pn="section-3.5-1">A number of keys are defined to indicate the quality of the clock that was
used to determine the point in time.</t>
        <t indent="0" pn="section-3.5-2">The first three are analogous to <tt>clock-quality-grouping</tt> in
<xref target="RFC8575" format="default" sectionFormat="of" derivedContent="RFC8575"/>, which is in turn based on the definitions in
<xref target="IEEE1588-2008" format="default" sectionFormat="of" derivedContent="IEEE1588-2008"/>; the last two are specific to this document.</t>
        <sourcecode type="cddl" markers="false" pn="section-3.5-3">
ClockQuality-group = (
  ? &amp;(ClockClass: -2) =&gt; uint .size 1 ; PTP/RFC8575
  ? &amp;(ClockAccuracy: -4) =&gt; uint .size 1 ; PTP/RFC8575
  ? &amp;(OffsetScaledLogVariance: -5) =&gt; uint .size 2 ; PTP/RFC8575
  ? &amp;(Uncertainty: -7) =&gt; ~time/~duration
  ? &amp;(Guarantee: -8) =&gt; ~time/~duration
)
</sourcecode>
        <section anchor="clockclass-key-2" numbered="true" removeInRFC="false" toc="include" pn="section-3.5.1">
          <name slugifiedName="name-clockclass-key-2">ClockClass (Key -2)</name>
          <t indent="0" pn="section-3.5.1-1">Key -2 (ClockClass) can be used to indicate the clock class as per
<xref target="RFC8575" format="default" sectionFormat="of" derivedContent="RFC8575"/> (which is based on Table 5 in Section 7.6.2.4 of <xref target="IEEE1588-2008" format="default" sectionFormat="of" derivedContent="IEEE1588-2008"/>; Table 4 in Section 7.6.2.5 of <xref target="IEEE1588-2019" format="default" sectionFormat="of" derivedContent="IEEE1588-2019"/> has updated language).
It is defined as a one-byte unsigned integer as that is the range
defined in IEEE 1588.</t>
        </section>
        <section anchor="clockaccuracy-key-4" numbered="true" removeInRFC="false" toc="include" pn="section-3.5.2">
          <name slugifiedName="name-clockaccuracy-key-4">ClockAccuracy (Key -4)</name>
          <t indent="0" pn="section-3.5.2-1">Key -4 (ClockAccuracy) can be used to indicate the clock accuracy as
per <xref target="RFC8575" format="default" sectionFormat="of" derivedContent="RFC8575"/> (which is based on Table 6 in Section 7.6.2.5 of <xref target="IEEE1588-2008" format="default" sectionFormat="of" derivedContent="IEEE1588-2008"/>; additional values have been defined in Table 5 in
Section 7.6.2.6 of <xref target="IEEE1588-2019" format="default" sectionFormat="of" derivedContent="IEEE1588-2019"/>).
It is defined as a one-byte unsigned integer as that is the range defined there.
The range between 23 and 47 is a slightly distorted logarithmic scale
from 1 ps to 1 s in <xref target="IEEE1588-2019" format="default" sectionFormat="of" derivedContent="IEEE1588-2019"/> (in <xref target="IEEE1588-2008" format="default" sectionFormat="of" derivedContent="IEEE1588-2008"/>, the range was
a subset of that, 32 to 47 for 25 ns to 1 s) -- see
<xref target="formula-accuracy-enum" format="default" sectionFormat="of" derivedContent="Figure 3"/>; the number 254 is the
value to be used if an unknown accuracy needs to be expressed.</t>
          <figure anchor="formula-accuracy-enum" align="left" suppress-title="false" pn="figure-3">
            <name slugifiedName="name-approximate-conversion-from">Approximate Conversion from Accuracy to Accuracy Enumeration Value</name>
            <artset pn="section-3.5.2-2.1">
              <artwork type="svg" align="left" pn="section-3.5.2-2.1.1"><svg xmlns:xlink="http://www.w3.org/1999/xlink" xmlns="http://www.w3.org/2000/svg" height="4.676ex" role="img" viewBox="0 -1221.9 14098.6 2013.3" width="32.745ex">
                  <defs>
                    <path d="M363 112l14 -13c-70 -86 -138 -110 -200 -110c-98 0 -137 84 -137 156c0 23 1 37 6 60c25 111 135 236 262 236c42 0 102 -14 102 -76c0 -127 -167 -176 -286 -182v-28c0 -64 52 -107 113 -107c42 0 90 18 126 64zM124 211h9c104 0 198 69 198 157c0 25 -19 43 -44 43 c-74 0 -134 -115 -163 -200Z" id="E1-STIXWEBNORMALI-1D452-gensym002" stroke-width="1"/>
                    <path d="M467 96l-5 -6c-28 -34 -76 -98 -128 -98c-32 0 -41 23 -41 46c0 13 4 29 7 40l57 221c2 8 7 28 7 42c0 19 -6 38 -24 38c-38 0 -101 -86 -132 -133c-36 -54 -62 -101 -68 -122l-33 -124h-77l95 374c0 18 -3 32 -30 32c-10 0 -21 -2 -28 -3l-2 15l159 23l-51 -189h3 c5 0 54 70 56 73c40 50 100 116 160 116c44 0 56 -29 56 -62c0 -25 -6 -50 -11 -70l-59 -231c-1 -2 -1 -5 -1 -10c1 -6 4 -14 15 -14c24 0 48 36 62 53Z" id="E1-STIXWEBNORMALI-1D45B-gensym002" stroke-width="1"/>
                    <path d="M444 428l-89 -348c-1 -4 -1 -6 -1 -9c0 -8 4 -14 14 -14c21 0 40 26 57 46l5 6l13 -11c-23 -33 -74 -107 -132 -107c-29 0 -40 19 -40 52c0 9 1 25 4 37l26 95h-1c-7 -5 -97 -126 -137 -156c-23 -17 -49 -28 -72 -28c-47 0 -61 36 -61 74c0 21 3 40 8 59l59 231 c4 15 6 21 6 25c0 12 -11 23 -33 23c-7 0 -19 -1 -26 -3l-3 15l157 26l-84 -326c-2 -9 -3 -16 -3 -24c0 -21 8 -34 26 -34c25 0 65 31 100 77c43 57 89 146 109 219l21 75h77Z" id="E1-STIXWEBNORMALI-1D462-gensym002" stroke-width="1"/>
                    <path d="M667 107l13 -11c-32 -54 -84 -104 -131 -104c-22 0 -39 10 -39 49c0 7 1 17 6 37l56 221c4 14 6 23 6 40c0 20 -6 38 -24 38c-54 0 -164 -181 -179 -242l-34 -135h-79l77 299c2 9 5 25 5 40c0 20 -5 38 -23 38c-52 0 -162 -181 -178 -242l-35 -135h-78l95 374 c0 18 -6 31 -33 31c-8 0 -19 -1 -27 -2l-2 14l157 24l-44 -169h6c94 143 154 169 192 169c37 0 55 -37 55 -81c0 -17 -3 -32 -9 -52l-10 -36h5c29 52 81 114 130 147c22 15 41 22 61 22c36 0 54 -26 54 -71c0 -18 -1 -37 -7 -61l-61 -231c-1 -3 -2 -9 -2 -12 c0 -8 6 -12 15 -12c17 0 43 16 62 53Z" id="E1-STIXWEBNORMALI-1D45A-gensym002" stroke-width="1"/>
                    <path d="M472 428l-91 -345s-1 -2 -1 -11c0 -11 6 -17 14 -17c10 0 25 2 64 54l12 -12c-31 -47 -85 -107 -133 -107c-33 0 -42 23 -42 55c0 13 6 34 11 50h-4c-72 -92 -134 -105 -173 -105c-63 0 -89 55 -89 119c0 132 132 332 276 332c43 0 64 -24 66 -46h1l9 33h80zM367 341 c0 41 -12 71 -50 71c-68 0 -128 -87 -162 -171c-18 -45 -28 -89 -28 -124c0 -53 31 -66 58 -66c69 0 139 95 167 190c8 26 15 66 15 100Z" id="E1-STIXWEBNORMALI-1D44E-gensym002" stroke-width="1"/>
                    <path d="M363 111l12 -13c-51 -60 -113 -109 -198 -109c-97 0 -137 78 -137 155c0 140 121 297 263 297c50 0 97 -27 97 -76c0 -38 -16 -70 -54 -70c-26 0 -38 21 -38 38c0 24 29 36 29 58c0 12 -10 21 -34 21c-119 0 -176 -179 -176 -259c0 -87 49 -109 94 -109 c61 0 107 33 142 67Z" id="E1-STIXWEBNORMALI-1D450-gensym002" stroke-width="1"/>
                    <path d="M604 475h33c-6 -85 -60 -204 -158 -204c-96 0 -203 128 -275 128c-70 0 -107 -67 -123 -138h-33c5 100 65 204 163 204c96 0 203 -128 276 -128c69 0 102 67 117 138zM604 239h33c-6 -85 -60 -204 -158 -204c-96 0 -203 128 -275 128c-70 0 -107 -67 -123 -138h-33 c5 100 65 204 163 204c96 0 203 -128 276 -128c69 0 102 67 117 138Z" id="E1-STIXWEBMAIN-2248-gensym002" stroke-width="1"/>
                    <path d="M473 167h-103v-167h-78v167h-280v64l314 445h44v-445h103v-64zM292 231v343l-240 -343h240Z" id="E1-STIXWEBMAIN-34-gensym002" stroke-width="1"/>
                    <path d="M445 155c0 -103 -77 -169 -197 -169c-113 0 -192 69 -192 163c0 69 23 108 130 183c-103 85 -124 123 -124 188c0 96 83 156 194 156c99 0 168 -65 168 -143c0 -75 -35 -109 -134 -162c123 -82 155 -136 155 -216zM355 533c0 69 -41 115 -109 115 c-67 0 -110 -37 -110 -99s37 -108 125 -160c68 40 94 82 94 144zM271 272l-59 40c-59 -48 -80 -89 -80 -154c0 -92 51 -144 127 -144c65 0 110 45 110 110c0 62 -30 102 -98 148Z" id="E1-STIXWEBMAIN-38-gensym002" stroke-width="1"/>
                    <path d="M636 220h-261v-261h-66v261h-261v66h261v261h66v-261h261v-66Z" id="E1-STIXWEBMAIN-2B-gensym002" stroke-width="1"/>
                    <path d="M447 -213h-259v926h66v-798c0 -64 19 -95 84 -95h109v-33Z" id="E1-STIXWEBMAIN-230A-gensym002" stroke-width="1"/>
                    <path d="M474 137l-54 -137h-391v12l178 189c94 99 130 175 130 260c0 91 -54 141 -139 141c-72 0 -107 -32 -147 -130l-21 5c21 117 85 199 208 199c113 0 185 -77 185 -176c0 -79 -39 -154 -128 -248l-165 -176h234c42 0 63 11 96 67Z" id="E1-STIXWEBMAIN-32-gensym002" stroke-width="1"/>
                    <path d="M203 253c0 -32 -27 -60 -59 -60c-33 0 -61 30 -61 60s28 60 61 60c32 0 59 -28 59 -60Z" id="E1-STIXWEBMAIN-22C5-gensym002" stroke-width="1"/>
                    <path d="M278 668l-148 -591s-1 -4 -1 -11s4 -13 12 -13c23 0 53 39 62 55l16 -12c-34 -40 -77 -106 -135 -106c-30 0 -39 26 -39 51c0 12 3 26 6 36l128 510c3 13 3 21 3 24c0 12 -8 22 -31 22c-7 0 -19 -2 -27 -3l-3 15Z" id="E1-STIXWEBNORMALI-1D459-gensym002" stroke-width="1"/>
                    <path d="M438 287c0 -139 -110 -298 -263 -298c-101 0 -135 90 -135 163c0 128 103 289 251 289c80 0 147 -46 147 -154zM357 318c0 38 -14 93 -67 93c-82 0 -169 -149 -169 -285c0 -33 3 -107 59 -107c106 0 177 223 177 299Z" id="E1-STIXWEBNORMALI-1D45C-gensym002" stroke-width="1"/>
                    <path d="M492 413l-13 -45h-81c13 -15 17 -28 17 -50c0 -75 -53 -137 -141 -148c-59 -8 -88 -33 -88 -58c0 -63 233 -23 233 -148c0 -71 -66 -151 -215 -151c-134 0 -184 57 -184 115s55 88 117 108c-17 11 -24 30 -24 47c0 38 37 87 85 87v4c-67 15 -94 62 -94 109 c0 79 68 158 174 158c42 0 73 -13 88 -28h126zM336 349c0 37 -10 62 -54 62c-54 0 -98 -71 -98 -139c0 -46 12 -81 56 -81c71 0 96 102 96 158zM349 -69c0 78 -132 73 -192 95c-8 -5 -18 -10 -26 -16c-26 -19 -48 -45 -48 -72c0 -47 44 -97 139 -97c91 0 127 46 127 90Z" id="E1-STIXWEBNORMALI-1D454-gensym002" stroke-width="1"/>
                    <path d="M394 0h-276v15c74 4 95 25 95 80v449c0 34 -9 49 -30 49c-10 0 -27 -5 -45 -12l-27 -10v14l179 91l9 -3v-597c0 -43 20 -61 95 -61v-15Z" id="E1-STIXWEBMAIN-31-gensym002" stroke-width="1"/>
                    <path d="M476 330c0 -172 -63 -344 -226 -344c-171 0 -226 186 -226 350c0 177 69 340 230 340c131 0 222 -141 222 -346zM380 325c0 208 -44 325 -132 325c-83 0 -128 -118 -128 -321s44 -317 130 -317c85 0 130 115 130 313Z" id="E1-STIXWEBMAIN-30-gensym002" stroke-width="1"/>
                    <path d="M156 301l104 -63c64 -39 88 -66 88 -123c0 -67 -64 -125 -140 -125c-21 0 -50 1 -73 9c-24 8 -35 9 -46 9c-12 0 -18 -2 -24 -12h-13v157h16c21 -97 58 -141 127 -141c51 0 83 33 83 74c0 31 -20 57 -53 75l-54 30c-83 46 -120 94 -120 145c0 79 56 123 138 123 c24 0 46 -1 67 -11c11 -5 21 -8 28 -8c4 0 8 1 16 10h11l5 -136h-15c-23 90 -53 123 -113 123c-43 0 -75 -21 -75 -68c0 -22 15 -51 43 -68Z" id="E1-STIXWEBMAIN-73-gensym002" stroke-width="1"/>
                    <path d="M621 220h-557v66h557v-66Z" id="E1-STIXWEBMAIN-2212-gensym002" stroke-width="1"/>
                    <path d="M444 372l-14 -8c-25 36 -60 47 -120 47c-63 0 -139 -44 -139 -113c0 -32 33 -51 78 -51c21 0 37 9 62 9c22 0 38 -7 38 -20c0 -17 -10 -31 -43 -31c-9 0 -40 6 -61 6c-49 0 -133 -33 -133 -103c0 -61 65 -78 125 -78c53 0 118 26 151 73l13 -10 c-42 -59 -99 -104 -210 -104c-124 0 -166 50 -166 102c0 73 49 120 116 137c-35 12 -58 33 -58 66c0 81 83 147 225 147c62 0 123 -33 136 -69Z" id="E1-STIXWEBNORMALI-1D700-gensym002" stroke-width="1"/>
                    <path d="M286 -213h-259v33h109c65 0 84 31 84 95v798h66v-926Z" id="E1-STIXWEBMAIN-230B-gensym002" stroke-width="1"/>
                  </defs>
                  <g fill="black" stroke="currentColor" stroke-width="0" transform="matrix(1 0 0 -1 0 0)">
                    <use xlink:href="#E1-STIXWEBNORMALI-1D452-gensym002" x="0" y="0"/>
                    <use xlink:href="#E1-STIXWEBNORMALI-1D45B-gensym002" x="445" y="0"/>
                    <use xlink:href="#E1-STIXWEBNORMALI-1D462-gensym002" x="943" y="0"/>
                    <g transform="translate(1417,0)">
                      <use xlink:href="#E1-STIXWEBNORMALI-1D45A-gensym002" x="0" y="0"/>
                      <g transform="translate(710,-150)">
                        <use xlink:href="#E1-STIXWEBNORMALI-1D44E-gensym002" transform="scale(0.707)" x="0" y="0"/>
                        <use xlink:href="#E1-STIXWEBNORMALI-1D450-gensym002" transform="scale(0.707)" x="502" y="0"/>
                        <use xlink:href="#E1-STIXWEBNORMALI-1D450-gensym002" transform="scale(0.707)" x="918" y="0"/>
                      </g>
                    </g>
                    <use xlink:href="#E1-STIXWEBMAIN-2248-gensym002" x="3448" y="0"/>
                    <g transform="translate(4411,0)">
                      <use xlink:href="#E1-STIXWEBMAIN-34-gensym002"/>
                      <use xlink:href="#E1-STIXWEBMAIN-38-gensym002" x="500" y="0"/>
                    </g>
                    <use xlink:href="#E1-STIXWEBMAIN-2B-gensym002" x="5635" y="0"/>
                    <use xlink:href="#E1-STIXWEBMAIN-230A-gensym002" x="6542" y="0"/>
                    <use xlink:href="#E1-STIXWEBMAIN-32-gensym002" x="7012" y="0"/>
                    <use xlink:href="#E1-STIXWEBMAIN-22C5-gensym002" x="7735" y="0"/>
                    <use xlink:href="#E1-STIXWEBNORMALI-1D459-gensym002" x="8243" y="0"/>
                    <use xlink:href="#E1-STIXWEBNORMALI-1D45C-gensym002" x="8562" y="0"/>
                    <g transform="translate(9020,0)">
                      <use xlink:href="#E1-STIXWEBNORMALI-1D454-gensym002" x="0" y="0"/>
                      <g transform="translate(492,-150)">
                        <use xlink:href="#E1-STIXWEBMAIN-31-gensym002" transform="scale(0.707)"/>
                        <use xlink:href="#E1-STIXWEBMAIN-30-gensym002" transform="scale(0.707)" x="500" y="0"/>
                      </g>
                    </g>
                    <g transform="translate(10321,0)">
                      <g transform="translate(120,0)">
                        <rect height="60" width="1453" x="0" y="220"/>
                        <g transform="translate(60,676)">
                          <use xlink:href="#E1-STIXWEBNORMALI-1D44E-gensym002" x="0" y="0"/>
                          <use xlink:href="#E1-STIXWEBNORMALI-1D450-gensym002" x="502" y="0"/>
                          <use xlink:href="#E1-STIXWEBNORMALI-1D450-gensym002" x="918" y="0"/>
                        </g>
                        <use xlink:href="#E1-STIXWEBMAIN-73-gensym002" x="532" y="-686"/>
                      </g>
                    </g>
                    <use xlink:href="#E1-STIXWEBMAIN-2212-gensym002" x="12236" y="0"/>
                    <use xlink:href="#E1-STIXWEBNORMALI-1D700-gensym002" x="13144" y="0"/>
                    <use xlink:href="#E1-STIXWEBMAIN-230B-gensym002" x="13629" y="0"/>
                  </g>
                </svg>
              </artwork>
              <artwork type="ascii-art" align="left" pn="section-3.5.2-2.1.2">                         acc
enum    ≈ 48 + ⌊2 ⋅log   ──── - ε⌋
    acc               10  s
</artwork>
            </artset>
          </figure>
        </section>
        <section anchor="offsetscaledlogvariance-key-5" numbered="true" removeInRFC="false" toc="include" pn="section-3.5.3">
          <name slugifiedName="name-offsetscaledlogvariance-key">OffsetScaledLogVariance (Key -5)</name>
          <t indent="0" pn="section-3.5.3-1">Key -5 (OffsetScaledLogVariance) can be used to represent the variance
exhibited by the clock when it has lost its synchronization with an
external reference clock.  The details for the computation of this
characteristic are defined in Section 7.6.3 of <xref target="IEEE1588-2019" format="default" sectionFormat="of" derivedContent="IEEE1588-2019"/> and the
same section in <xref target="IEEE1588-2008" format="default" sectionFormat="of" derivedContent="IEEE1588-2008"/>.</t>
        </section>
        <section anchor="uncertainty-key-7" numbered="true" removeInRFC="false" toc="include" pn="section-3.5.4">
          <name slugifiedName="name-uncertainty-key-7">Uncertainty (Key -7)</name>
          <t indent="0" pn="section-3.5.4-1">Key -7 (Uncertainty) can be used to represent a known uncertainty of measurement for the clock as a numeric value in seconds or as a
	  duration (<xref target="duration" format="default" sectionFormat="of" derivedContent="Section 4"/>).</t>
          <t indent="0" pn="section-3.5.4-2">For this document, uncertainty is defined as in Section 2.2.3 of <xref target="GUM" format="default" sectionFormat="of" derivedContent="GUM"/>: "parameter, associated with the result of a measurement, that
characterizes the dispersion of the values that could reasonably be
attributed to the measurand".  More specifically, the value for this
key represents the expanded uncertainty for k = 2 (Section 6.2.1 of <xref target="GUM" format="default" sectionFormat="of" derivedContent="GUM"/>) in seconds.</t>
          <t indent="0" pn="section-3.5.4-3">Note that the additional information that can be meaningfully provided
with the duration that represents an uncertainty is limited, e.g., it
is not customary to provide an uncertainty for a duration representing
an uncertainty.
Implementations are free to reduce the information contained in an
uncertainty (which is already elective) to the information they can
process.</t>
          <t indent="0" pn="section-3.5.4-4">For example, a timestamp that is given to a resolution of
10<sup>-6</sup> seconds (microseconds) but only has an uncertainty of
10<sup>-3</sup> seconds (milliseconds) could be expressed by one of
the extended time tags in <xref target="uncertainty-example" format="default" sectionFormat="of" derivedContent="Figure 4"/> (note the slight
rounding error in the third case, which is probably inconsequential
for an uncertainty value):</t>
          <figure anchor="uncertainty-example" align="left" suppress-title="false" pn="figure-4">
            <name slugifiedName="name-examples-using-uncertainty">Examples Using Uncertainty</name>
            <sourcecode type="cbor-diag" markers="false" pn="section-3.5.4-5.1">
1001({1: 1697724754, -6: 873294, -7: {1: 0, -6: 1000}}),
1001({1: 1697724754, -6: 873294, -7: {1: 0, -3: 1}}),
1001({1: 1697724754, -6: 873294, -7: {1: 0.001}})
</sourcecode>
          </figure>
        </section>
        <section anchor="guarantee-key-8" numbered="true" removeInRFC="false" toc="include" pn="section-3.5.5">
          <name slugifiedName="name-guarantee-key-8">Guarantee (Key -8)</name>
          <t indent="0" pn="section-3.5.5-1">Key -8 (Guarantee) can be used to represent a stated guarantee for the
accuracy of the point in time as a numeric value in seconds or as a
duration (<xref target="duration" format="default" sectionFormat="of" derivedContent="Section 4"/>)
representing the maximum allowed deviation from the true value.</t>
          <t indent="0" pn="section-3.5.5-2">While such a guarantee is unattainable in theory, existing standards
such as <xref target="RFC3161" format="default" sectionFormat="of" derivedContent="RFC3161"/> stipulate the representation of such guarantees,
and therefore this format provides a way to represent them as well;
the time value given is nominally guaranteed to not deviate from the
actual time by more than the value of the guarantee in seconds.</t>
          <t indent="0" pn="section-3.5.5-3">Note that the additional information that can be meaningfully provided
with the duration that represents a guarantee is limited, e.g., it is
not meaningful to provide a guarantee of accuracy for the duration
representing a guarantee of accuracy.
Implementations are free to reduce a guarantee (which is already
elective) to the information they can process.</t>
        </section>
      </section>
      <section anchor="tzh" numbered="true" removeInRFC="false" toc="include" pn="section-3.6">
        <name slugifiedName="name-keys-10-10-time-zone-hint">Keys -10, 10: Time Zone Hint</name>
        <t indent="0" pn="section-3.6-1">Keys -10 and 10 supply supplementary information, where key 10 is critical.</t>
        <t indent="0" pn="section-3.6-2">They can be used to provide a hint about the time zone that
would best fit for displaying the time given to humans, using a text
string in the format defined for <tt>time-zone-name</tt> or <tt>time-numoffset</tt>
in <xref target="RFC9557" format="default" sectionFormat="of" derivedContent="RFC9557"/>.
Key -10 is equivalent to providing this information as an elective
hint, while key 10 provides this information as critical (i.e., it
<bcp14>MUST</bcp14> be used when interpreting the entry with this key).</t>
        <t indent="0" pn="section-3.6-3">Keys -10 and 10 <bcp14>MUST NOT</bcp14> both be present.</t>
        <sourcecode type="cddl" markers="false" pn="section-3.6-4">
$$ETIME-ELECTIVE //= (-10: time-zone-info)
$$ETIME-CRITICAL //= (10: time-zone-info)

time-zone-info = tstr .abnf
                 ("time-zone-name / time-numoffset" .det IXDTFtz)
IXDTFtz = '
   time-hour       = 2DIGIT  ; 00-23
   time-minute     = 2DIGIT  ; 00-59
   time-numoffset  = ("+" / "-") time-hour ":" time-minute

   time-zone-initial = ALPHA / "." / "_"
   time-zone-char    = time-zone-initial / DIGIT / "-" / "+"
   time-zone-part    = time-zone-initial *time-zone-char
                       ; but not "." or ".."
   time-zone-name    = time-zone-part *("/" time-zone-part)
   ALPHA             =  %x41-5A / %x61-7A   ; A-Z / a-z
   DIGIT             =  %x30-39 ; 0-9
' ; extracted from [RFC9557] and [RFC3339]
</sourcecode>
      </section>
      <section anchor="suff" numbered="true" removeInRFC="false" toc="include" pn="section-3.7">
        <name slugifiedName="name-keys-11-11-ixdtf-suffix-inf">Keys -11, 11: IXDTF Suffix Information</name>
        <t indent="0" pn="section-3.7-1">Keys -11 and 11 supply supplementary information, where key 11 is critical.</t>
        <t indent="0" pn="section-3.7-2">Similar to keys -10 and 10, keys -11 (elective) and 11 (critical) can
be used to provide additional information in the style of Internet Extended Date/Time Format (IXDTF)
suffixes, such as the calendar that would best fit for displaying the
time given to humans.
The key's value is a map that has IXDTF <tt>suffix-key</tt> names as keys and
	corresponding suffix values as values, specifically:</t>
        <sourcecode type="cddl" markers="false" pn="section-3.7-3">
$$ETIME-ELECTIVE //= (-11: suffix-info-map)
$$ETIME-CRITICAL //= (11: suffix-info-map)

suffix-info-map = { * suffix-key =&gt; suffix-values }
suffix-key = tstr .abnf ("suffix-key" .det IXDTF)
suffix-values = one-or-more&lt;suffix-value&gt;
one-or-more&lt;T&gt; = T / [ 2* T ]
suffix-value = tstr .abnf ("suffix-value" .det IXDTF)

IXDTF = '
   key-initial       = lcalpha / "_"
   key-char          = key-initial / DIGIT / "-"
   suffix-key        = key-initial *key-char

   suffix-value      = 1*alphanum
   alphanum          = ALPHA / DIGIT
   lcalpha           =  %x61-7A
   ALPHA             =  %x41-5A / %x61-7A   ; A-Z / a-z
   DIGIT             =  %x30-39 ; 0-9
' ; extracted from [RFC9557]
</sourcecode>
        <t indent="0" pn="section-3.7-4">When keys -11 and 11 are both present, the two maps <bcp14>MUST NOT</bcp14> have
entries with the same map keys.</t>
        <t indent="0" pn="section-3.7-5">Figure 4 of <xref target="RFC9557" format="default" sectionFormat="of" derivedContent="RFC9557"/> gives an example for an extended date-time with both time zone
	and suffix information:</t>
        <artwork align="left" pn="section-3.7-6">
1996-12-19T16:39:57-08:00[America/Los_Angeles][u-ca=hebrew]
</artwork>
        <t indent="0" pn="section-3.7-7">A time tag that is approximating this example, in CBOR diagnostic
notation, would be:</t>
        <sourcecode type="cbor-diag" markers="false" pn="section-3.7-8">
/ 1996-12-19T16:39:57-08:00[America//Los_Angeles][u-ca=hebrew] /
1001({ 1: 851042397,
     -10: "America/Los_Angeles",
     -11: { "u-ca": "hebrew" }
})
</sourcecode>
        <t indent="0" pn="section-3.7-9">Note that both -10 and -11 are using negative keys and therefore
provide elective information, as in the IXDTF form given in the comment.
Also note that, in this example, the time numeric offset (<tt>-08:00</tt>) is
lost in translating from the <xref target="RFC3339" format="default" sectionFormat="of" derivedContent="RFC3339"/> information in the IXDTF into a
POSIX time that can be included under key 1 in a time tag.</t>
      </section>
    </section>
    <section anchor="duration" numbered="true" removeInRFC="false" toc="include" pn="section-4">
      <name slugifiedName="name-duration-format">Duration Format</name>
      <t indent="0" pn="section-4-1">A duration is the length of an interval of time.
Durations in this format are given in International System of Units (SI) seconds, possibly adjusted
for conventional corrections of the timescale given (e.g., leap
seconds).</t>
      <t indent="0" pn="section-4-2">Except for using tag 1002 instead of 1001,
durations are structurally identical to time values.</t>
      <sourcecode type="cddl" markers="false" pn="section-4-3">
Duration = #6.1002(etime-detailed)
</sourcecode>
      <t indent="0" pn="section-4-4">Semantically, they do not measure the time elapsed from a given epoch
but from the start to the end of an (otherwise unspecified) interval
of time.</t>
      <t indent="0" pn="section-4-5">In combination with an epoch identified in the context, a duration can
also be used to express an absolute time.</t>
      <t indent="0" pn="section-4-6">Without such context, durations are subject to some uncertainties
underlying the timescale used.
For example, for durations intended as a determinant of future time periods,
there is some uncertainty of what irregularities (such as leap
seconds and timescale corrections) will be exhibited by the timescale in
that period.
For durations as measurements of past periods, abstracting the period
to a duration loses some detail about timescale irregularities.
For many applications, these uncertainties are acceptable and thus
the use of durations is appropriate.</t>
      <aside pn="section-4-7">
        <t indent="0" pn="section-4-7.1">Note that the durations defined in <xref target="ISO8601" format="default" sectionFormat="of" derivedContent="ISO8601:1988"/> and <xref target="ISO8601-2019" format="default" sectionFormat="of" derivedContent="ISO8601-1:2019"/> are rather different from the ones defined
in the present specification; there is no intention to support ISO 8601
durations here.</t>
      </aside>
    </section>
    <section anchor="period" numbered="true" removeInRFC="false" toc="include" pn="section-5">
      <name slugifiedName="name-period-format">Period Format</name>
      <t indent="0" pn="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.</t>
      <t indent="0" pn="section-5-2">This is represented as an array of unwrapped time and duration elements,
tagged with tag 1003, one of:</t>
      <ul spacing="normal" bare="false" empty="false" indent="3" pn="section-5-3">
        <li pn="section-5-3.1">
          <t indent="0" pn="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, or</t>
        </li>
        <li pn="section-5-3.2">
          <t indent="0" pn="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 <bcp14>MUST</bcp14> be set to null and the
third one then is an unwrapped duration.</t>
        </li>
      </ul>
      <t indent="0" pn="section-5-4">A simple CDDL definition that does not capture all the constraints is:</t>
      <sourcecode type="cddl" markers="false" pn="section-5-5">
simple-Period = #6.1003([
  start: ~Etime / null
  end: ~Etime / null
  ? duration: ~Duration
])
</sourcecode>
      <t indent="0" pn="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:</t>
      <sourcecode type="cddl" markers="false" pn="section-5-7">
Period = #6.1003([
  (start: ~Etime,
   ((end: ~Etime) //
    (end: null,
     duration: ~Duration))) //
  (start: null,
   end: ~Etime,
   duration: ~Duration)
])
</sourcecode>
    </section>
    <section anchor="cddl-typenames" numbered="true" removeInRFC="false" toc="include" pn="section-6">
      <name slugifiedName="name-cddl-type-names">CDDL Type Names</name>
      <t indent="0" pn="section-6-1">When detailed validation is not needed, the
type names defined in <xref target="tag-cddl" format="default" sectionFormat="of" derivedContent="Figure 5"/> are recommended:</t>
      <figure anchor="tag-cddl" align="left" suppress-title="false" pn="figure-5">
        <name slugifiedName="name-recommended-type-names-for-">Recommended Type Names for CDDL</name>
        <sourcecode type="cddl" markers="false" pn="section-6-2.1">
etime = #6.1001({* (int/tstr) =&gt; any})
duration = #6.1002({* (int/tstr) =&gt; any})
period = #6.1003([~etime/null, ~etime/null, ?~duration])
</sourcecode>
      </figure>
    </section>
    <section anchor="iana-considerations" numbered="true" removeInRFC="false" toc="include" pn="section-7">
      <name slugifiedName="name-iana-considerations">IANA Considerations</name>
      <section anchor="cbor-tags" numbered="true" removeInRFC="false" toc="include" pn="section-7.1">
        <name slugifiedName="name-cbor-tags">CBOR Tags</name>
        <t indent="0" pn="section-7.1-1">In the "CBOR Tags" registry <xref target="IANA.cbor-tags" format="default" sectionFormat="of" derivedContent="IANA.cbor-tags"/>,
IANA has allocated the tags in <xref target="tab-tag-values" format="default" sectionFormat="of" derivedContent="Table 2"/>.</t>
        <table anchor="tab-tag-values" align="center" pn="table-2">
          <name slugifiedName="name-values-for-tags">Values for Tags</name>
          <thead>
            <tr>
              <th align="right" colspan="1" rowspan="1">Tag</th>
              <th align="left" colspan="1" rowspan="1">Data Item</th>
              <th align="left" colspan="1" rowspan="1">Semantics</th>
              <th align="left" colspan="1" rowspan="1">Reference</th>
            </tr>
          </thead>
          <tbody>
            <tr>
              <td align="right" colspan="1" rowspan="1">1001</td>
              <td align="left" colspan="1" rowspan="1">map</td>
              <td align="left" colspan="1" rowspan="1">extended time</td>
              <td align="left" colspan="1" rowspan="1">[RFC9581, <xref target="time-format" format="default" sectionFormat="of" derivedContent="Section 3"/>]</td>
            </tr>
            <tr>
              <td align="right" colspan="1" rowspan="1">1002</td>
              <td align="left" colspan="1" rowspan="1">map</td>
              <td align="left" colspan="1" rowspan="1">duration</td>
              <td align="left" colspan="1" rowspan="1">[RFC9581, <xref target="duration" format="default" sectionFormat="of" derivedContent="Section 4"/>]</td>
            </tr>
            <tr>
              <td align="right" colspan="1" rowspan="1">1003</td>
              <td align="left" colspan="1" rowspan="1">array</td>
              <td align="left" colspan="1" rowspan="1">period</td>
              <td align="left" colspan="1" rowspan="1">[RFC9581, <xref target="period" format="default" sectionFormat="of" derivedContent="Section 5"/>]</td>
            </tr>
          </tbody>
        </table>
        <t indent="0" pn="section-7.1-3">IANA has updated the "Data Item" column for tag 1003 from
"map" to "array".</t>
      </section>
      <section anchor="timescale-registry" numbered="true" removeInRFC="false" toc="include" pn="section-7.2">
        <name slugifiedName="name-timescales-registry">Timescales Registry</name>
        <t indent="0" pn="section-7.2-1">Per this specification, IANA has created a new "Timescales" registry within the
"Concise Binary Object Representation (CBOR) Tags" registry group <xref target="IANA.cbor-tags" format="default" sectionFormat="of" derivedContent="IANA.cbor-tags"/>.  The registration procedure requires both 
"Expert Review" and "RFC Required" (Sections <xref section="4.5" sectionFormat="bare" target="RFC8126" format="default" derivedLink="https://rfc-editor.org/rfc/rfc8126#section-4.5" derivedContent="RFC8126"/> and 
<xref section="4.7" sectionFormat="bare" target="RFC8126" format="default" derivedLink="https://rfc-editor.org/rfc/rfc8126#section-4.7" derivedContent="RFC8126"/> of RFC 8126 <xref target="BCP26" format="default" sectionFormat="of" derivedContent="BCP26"/>, respectively).</t>
        <t indent="0" pn="section-7.2-2">Each entry needs to provide a timescale name (a sequence of uppercase
ASCII characters and digits, where a digit may not occur at the start:
<tt>[A-Z][A-Z0-9]*</tt>), a value (CBOR unsigned integer, uint,
0..18446744073709551615), a brief description
of the semantics, and a specification reference (RFC).
The initial contents are shown in <xref target="tab-timescales" format="default" sectionFormat="of" derivedContent="Table 3"/>.</t>
        <table anchor="tab-timescales" align="center" pn="table-3">
          <name slugifiedName="name-initial-content-of-timescal">Initial Content of Timescale Registry</name>
          <thead>
            <tr>
              <th align="left" colspan="1" rowspan="1">Timescale</th>
              <th align="right" colspan="1" rowspan="1">Value</th>
              <th align="left" colspan="1" rowspan="1">Semantics</th>
              <th align="left" colspan="1" rowspan="1">Reference</th>
            </tr>
          </thead>
          <tbody>
            <tr>
              <td align="left" colspan="1" rowspan="1">UTC</td>
              <td align="right" colspan="1" rowspan="1">0</td>
              <td align="left" colspan="1" rowspan="1">UTC with POSIX Epoch</td>
              <td align="left" colspan="1" rowspan="1">[RFC9581]</td>
            </tr>
            <tr>
              <td align="left" colspan="1" rowspan="1">TAI</td>
              <td align="right" colspan="1" rowspan="1">1</td>
              <td align="left" colspan="1" rowspan="1">TAI with PTP Epoch</td>
              <td align="left" colspan="1" rowspan="1">[RFC9581]</td>
            </tr>
          </tbody>
        </table>
      </section>
      <section anchor="map-key-registry" numbered="true" removeInRFC="false" toc="include" pn="section-7.3">
        <name slugifiedName="name-time-tag-map-keys-registry">Time Tag Map Keys Registry</name>
        <t indent="0" pn="section-7.3-1">Per this specification, IANA has created a new "Time Tag Map Keys" registry within the "Concise Binary Object Representation (CBOR) Tags" registry group <xref target="IANA.cbor-tags" format="default" sectionFormat="of" derivedContent="IANA.cbor-tags"/>.  The registration procedure  is "Specification
Required" (Section <xref section="4.6" sectionFormat="bare" target="RFC8126" format="default" derivedLink="https://rfc-editor.org/rfc/rfc8126#section-4.6" derivedContent="RFC8126"/> of RFC 8126 <xref target="BCP26" format="default" sectionFormat="of" derivedContent="BCP26"/>).</t>
        <t indent="0" pn="section-7.3-2">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.</t>
        <t indent="0" pn="section-7.3-3">Each entry needs to provide a map key value (CBOR integer, int,
-18446744073709551616..18446744073709551615), a brief description
of the semantics, and a specification reference.
Note that negative integers indicate an elective key, while unsigned
integers indicate a key that either provides a base time or is
critical. The designated expert is requested to discuss with the registrant
 whether or not it is desirable to register a pair of an elective and a
 critical key for the same information, where the elective key value
 is the negative of the critical key (similar to how for example -11
 and 11 have been assigned in <xref target="tab-mapkeys" format="default" sectionFormat="of" derivedContent="Table 4"/>).
For the unsigned integers as keys, the choice of base time or critical
needs to be indicated in the brief semantics description.
(Elective map keys may be explicitly marked as such in the
description, e.g., to distinguish them from critical keys.)</t>
        <t indent="0" pn="section-7.3-4">The initial contents are shown in <xref target="tab-mapkeys" format="default" sectionFormat="of" derivedContent="Table 4"/>.</t>
        <table anchor="tab-mapkeys" align="center" pn="table-4">
          <name slugifiedName="name-initial-content-of-time-tag">Initial Content of Time Tag Map Keys Registry</name>
          <thead>
            <tr>
              <th align="right" colspan="1" rowspan="1">Value</th>
              <th align="left" colspan="1" rowspan="1">Semantics</th>
              <th align="left" colspan="1" rowspan="1">Reference</th>
            </tr>
          </thead>
          <tbody>
            <tr>
              <td align="right" colspan="1" rowspan="1">-18</td>
              <td align="left" colspan="1" rowspan="1">attoseconds</td>
              <td align="left" colspan="1" rowspan="1">[RFC9581]</td>
            </tr>
            <tr>
              <td align="right" colspan="1" rowspan="1">-15</td>
              <td align="left" colspan="1" rowspan="1">femtoseconds</td>
              <td align="left" colspan="1" rowspan="1">[RFC9581]</td>
            </tr>
            <tr>
              <td align="right" colspan="1" rowspan="1">-13</td>
              <td align="left" colspan="1" rowspan="1">timescale (elective)</td>
              <td align="left" colspan="1" rowspan="1">[RFC9581]</td>
            </tr>
            <tr>
              <td align="right" colspan="1" rowspan="1">-12</td>
              <td align="left" colspan="1" rowspan="1">picoseconds</td>
              <td align="left" colspan="1" rowspan="1">[RFC9581]</td>
            </tr>
            <tr>
              <td align="right" colspan="1" rowspan="1">-11</td>
              <td align="left" colspan="1" rowspan="1">IXDTF Suffix Information (elective)</td>
              <td align="left" colspan="1" rowspan="1">[RFC9581], <xref target="RFC9557" format="default" sectionFormat="of" derivedContent="RFC9557"/></td>
            </tr>
            <tr>
              <td align="right" colspan="1" rowspan="1">-10</td>
              <td align="left" colspan="1" rowspan="1">IXDTF Time Zone Hint (elective)</td>
              <td align="left" colspan="1" rowspan="1">[RFC9581], <xref target="RFC9557" format="default" sectionFormat="of" derivedContent="RFC9557"/></td>
            </tr>
            <tr>
              <td align="right" colspan="1" rowspan="1">-9</td>
              <td align="left" colspan="1" rowspan="1">nanoseconds</td>
              <td align="left" colspan="1" rowspan="1">[RFC9581]</td>
            </tr>
            <tr>
              <td align="right" colspan="1" rowspan="1">-8</td>
              <td align="left" colspan="1" rowspan="1">Guarantee</td>
              <td align="left" colspan="1" rowspan="1">[RFC9581]</td>
            </tr>
            <tr>
              <td align="right" colspan="1" rowspan="1">-7</td>
              <td align="left" colspan="1" rowspan="1">Uncertainty</td>
              <td align="left" colspan="1" rowspan="1">[RFC9581]</td>
            </tr>
            <tr>
              <td align="right" colspan="1" rowspan="1">-6</td>
              <td align="left" colspan="1" rowspan="1">microseconds</td>
              <td align="left" colspan="1" rowspan="1">[RFC9581]</td>
            </tr>
            <tr>
              <td align="right" colspan="1" rowspan="1">-5</td>
              <td align="left" colspan="1" rowspan="1">Offset-Scaled Log Variance</td>
              <td align="left" colspan="1" rowspan="1">[RFC9581]</td>
            </tr>
            <tr>
              <td align="right" colspan="1" rowspan="1">-4</td>
              <td align="left" colspan="1" rowspan="1">Clock Accuracy</td>
              <td align="left" colspan="1" rowspan="1">[RFC9581]</td>
            </tr>
            <tr>
              <td align="right" colspan="1" rowspan="1">-3</td>
              <td align="left" colspan="1" rowspan="1">milliseconds</td>
              <td align="left" colspan="1" rowspan="1">[RFC9581]</td>
            </tr>
            <tr>
              <td align="right" colspan="1" rowspan="1">-2</td>
              <td align="left" colspan="1" rowspan="1">Clock Class</td>
              <td align="left" colspan="1" rowspan="1">[RFC9581]</td>
            </tr>
            <tr>
              <td align="right" colspan="1" rowspan="1">-1</td>
              <td align="left" colspan="1" rowspan="1">timescale (elective) legacy</td>
              <td align="left" colspan="1" rowspan="1">[RFC9581]</td>
            </tr>
            <tr>
              <td align="right" colspan="1" rowspan="1">1</td>
              <td align="left" colspan="1" rowspan="1">base time value as in CBOR tag 1</td>
              <td align="left" colspan="1" rowspan="1">
                <xref target="RFC8949" format="default" sectionFormat="of" derivedContent="RFC8949"/>, [RFC9581]</td>
            </tr>
            <tr>
              <td align="right" colspan="1" rowspan="1">4</td>
              <td align="left" colspan="1" rowspan="1">base time value as in CBOR tag 4</td>
              <td align="left" colspan="1" rowspan="1">
                <xref target="RFC8949" format="default" sectionFormat="of" derivedContent="RFC8949"/>, [RFC9581]</td>
            </tr>
            <tr>
              <td align="right" colspan="1" rowspan="1">5</td>
              <td align="left" colspan="1" rowspan="1">base time value as in CBOR tag 5</td>
              <td align="left" colspan="1" rowspan="1">
                <xref target="RFC8949" format="default" sectionFormat="of" derivedContent="RFC8949"/>, [RFC9581]</td>
            </tr>
            <tr>
              <td align="right" colspan="1" rowspan="1">10</td>
              <td align="left" colspan="1" rowspan="1">IXDTF Time Zone Hint (critical)</td>
              <td align="left" colspan="1" rowspan="1">
                <xref target="RFC9557" format="default" sectionFormat="of" derivedContent="RFC9557"/>, [RFC9581]</td>
            </tr>
            <tr>
              <td align="right" colspan="1" rowspan="1">11</td>
              <td align="left" colspan="1" rowspan="1">IXDTF Suffix Information (critical)</td>
              <td align="left" colspan="1" rowspan="1">
                <xref target="RFC9557" format="default" sectionFormat="of" derivedContent="RFC9557"/>, [RFC9581]</td>
            </tr>
            <tr>
              <td align="right" colspan="1" rowspan="1">13</td>
              <td align="left" colspan="1" rowspan="1">timescale (critical)</td>
              <td align="left" colspan="1" rowspan="1">[RFC9581]</td>
            </tr>
          </tbody>
        </table>
      </section>
    </section>
    <section anchor="security-considerations" numbered="true" removeInRFC="false" toc="include" pn="section-8">
      <name slugifiedName="name-security-considerations">Security Considerations</name>
      <t indent="0" pn="section-8-1">The security considerations of <xref target="RFC8949" format="default" sectionFormat="of" derivedContent="RFC8949"/> apply; the tags introduced
here are not expected to raise security considerations beyond those.</t>
      <t indent="0" pn="section-8-2">Time, of course, has significant security considerations; these
include the exploitation of ambiguities where time is security
relevant (e.g., for freshness or in a validity span) or the disclosure
of characteristics of the emitting system (e.g., time zone or clock
resolution and wall clock offset).</t>
      <t indent="0" pn="section-8-3">A more detailed discussion of security considerations emanating from
using a representation of time that allows the inclusion of complex and
possibly inconsistent information is available in "Security Considerations"
(<xref section="7" sectionFormat="of" target="RFC9557" format="default" derivedLink="https://rfc-editor.org/rfc/rfc9557#section-7" derivedContent="RFC9557"/>).</t>
    </section>
  </middle>
  <back>
    <displayreference target="ISO8601" to="ISO8601:1988"/>
    <displayreference target="ISO8601-2019" to="ISO8601-1:2019"/>
    <references pn="section-9">
      <name slugifiedName="name-references">References</name>
      <references anchor="sec-normative-references" pn="section-9.1">
        <name slugifiedName="name-normative-references">Normative References</name>
        <referencegroup anchor="BCP26" target="https://www.rfc-editor.org/info/bcp26" derivedAnchor="BCP26">
          <reference anchor="RFC8126" target="https://www.rfc-editor.org/info/rfc8126" quoteTitle="true">
            <front>
              <title>Guidelines for Writing an IANA Considerations Section in RFCs</title>
              <author fullname="M. Cotton" initials="M." surname="Cotton"/>
              <author fullname="B. Leiba" initials="B." surname="Leiba"/>
              <author fullname="T. Narten" initials="T." surname="Narten"/>
              <date month="June" year="2017"/>
              <abstract>
                <t indent="0">Many protocols make use of points of extensibility that use constants to identify various protocol parameters. To ensure that the values in these fields do not have conflicting uses and to promote interoperability, their allocations are often coordinated by a central record keeper. For IETF protocols, that role is filled by the Internet Assigned Numbers Authority (IANA).</t>
                <t indent="0">To make assignments in a given registry prudently, guidance describing the conditions under which new values should be assigned, as well as when and how modifications to existing values can be made, is needed. This document defines a framework for the documentation of these guidelines by specification authors, in order to assure that the provided guidance for the IANA Considerations is clear and addresses the various issues that are likely in the operation of a registry.</t>
                <t indent="0">This is the third edition of this document; it obsoletes RFC 5226.</t>
              </abstract>
            </front>
            <seriesInfo name="BCP" value="26"/>
            <seriesInfo name="RFC" value="8126"/>
            <seriesInfo name="DOI" value="10.17487/RFC8126"/>
          </reference>
        </referencegroup>
        <reference anchor="GUM" target="https://www.bipm.org/en/publications/guides/gum.html" quoteTitle="true" derivedAnchor="GUM">
          <front>
            <title>Evaluation of measurement data -- Guide to the expression of uncertainty in measurement</title>
            <author>
              <organization showOnFrontPage="true">Joint Committee for Guides in Metrology</organization>
            </author>
            <date month="September" year="2008"/>
          </front>
          <seriesInfo name="JCGM" value="100:2008"/>
        </reference>
        <reference anchor="IANA.cbor-tags" target="https://www.iana.org/assignments/cbor-tags" quoteTitle="true" derivedAnchor="IANA.cbor-tags">
          <front>
            <title>Concise Binary Object Representation (CBOR) Tags</title>
            <author>
              <organization showOnFrontPage="true">IANA</organization>
            </author>
          </front>
        </reference>
        <reference anchor="IEEE1588-2008" target="https://standards.ieee.org/ieee/1588/4355/" quoteTitle="true" derivedAnchor="IEEE1588-2008">
          <front>
            <title>IEEE Standard for a Precision Clock Synchronization Protocol for Networked Measurement and Control Systems</title>
            <author>
              <organization showOnFrontPage="true">IEEE</organization>
            </author>
            <date month="July" year="2008"/>
          </front>
          <seriesInfo name="IEEE" value="1588-2008"/>
          <annotation>Often called PTP v2, as it replaced the earlier 2002 version of this standard by a non-backwards compatible protocol.</annotation>
        </reference>
        <reference anchor="IEEE1588-2019" target="https://standards.ieee.org/ieee/1588/6825/" quoteTitle="true" derivedAnchor="IEEE1588-2019">
          <front>
            <title>IEEE Standard for a Precision Clock Synchronization Protocol for Networked Measurement and Control Systems</title>
            <author>
              <organization showOnFrontPage="true">IEEE</organization>
            </author>
            <date month="June" year="2020"/>
          </front>
          <seriesInfo name="IEEE" value="1588-2019"/>
          <annotation>Often called PTP v2.1, as it has been designed so it can be used in a way that is fully backwards compatible to IEEE1588-2008.</annotation>
        </reference>
        <reference anchor="RFC2119" target="https://www.rfc-editor.org/info/rfc2119" quoteTitle="true" derivedAnchor="RFC2119">
          <front>
            <title>Key words for use in RFCs to Indicate Requirement Levels</title>
            <author fullname="S. Bradner" initials="S." surname="Bradner"/>
            <date month="March" year="1997"/>
            <abstract>
              <t indent="0">In many standards track documents several words are used to signify the requirements in the specification. These words are often capitalized. This document defines these words as they should be interpreted in IETF documents. This document specifies an Internet Best Current Practices for the Internet Community, and requests discussion and suggestions for improvements.</t>
            </abstract>
          </front>
          <seriesInfo name="BCP" value="14"/>
          <seriesInfo name="RFC" value="2119"/>
          <seriesInfo name="DOI" value="10.17487/RFC2119"/>
        </reference>
        <reference anchor="RFC8174" target="https://www.rfc-editor.org/info/rfc8174" quoteTitle="true" derivedAnchor="RFC8174">
          <front>
            <title>Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words</title>
            <author fullname="B. Leiba" initials="B." surname="Leiba"/>
            <date month="May" year="2017"/>
            <abstract>
              <t indent="0">RFC 2119 specifies common key words that may be used in protocol specifications. This document aims to reduce the ambiguity by clarifying that only UPPERCASE usage of the key words have the defined special meanings.</t>
            </abstract>
          </front>
          <seriesInfo name="BCP" value="14"/>
          <seriesInfo name="RFC" value="8174"/>
          <seriesInfo name="DOI" value="10.17487/RFC8174"/>
        </reference>
        <reference anchor="RFC8575" target="https://www.rfc-editor.org/info/rfc8575" quoteTitle="true" derivedAnchor="RFC8575">
          <front>
            <title>YANG Data Model for the Precision Time Protocol (PTP)</title>
            <author fullname="Y. Jiang" initials="Y." role="editor" surname="Jiang"/>
            <author fullname="X. Liu" initials="X." surname="Liu"/>
            <author fullname="J. Xu" initials="J." surname="Xu"/>
            <author fullname="R. Cummings" initials="R." role="editor" surname="Cummings"/>
            <date month="May" year="2019"/>
            <abstract>
              <t indent="0">This document defines a YANG data model for the configuration of devices and clocks using the Precision Time Protocol (PTP) as specified in IEEE Std 1588-2008. It also defines the retrieval of the configuration information, the data sets and the running states of PTP clocks. The YANG module in this document conforms to the Network Management Datastore Architecture (NMDA).</t>
            </abstract>
          </front>
          <seriesInfo name="RFC" value="8575"/>
          <seriesInfo name="DOI" value="10.17487/RFC8575"/>
        </reference>
        <reference anchor="RFC8610" target="https://www.rfc-editor.org/info/rfc8610" quoteTitle="true" derivedAnchor="RFC8610">
          <front>
            <title>Concise Data Definition Language (CDDL): A Notational Convention to Express Concise Binary Object Representation (CBOR) and JSON Data Structures</title>
            <author fullname="H. Birkholz" initials="H." surname="Birkholz"/>
            <author fullname="C. Vigano" initials="C." surname="Vigano"/>
            <author fullname="C. Bormann" initials="C." surname="Bormann"/>
            <date month="June" year="2019"/>
            <abstract>
              <t indent="0">This document proposes a notational convention to express Concise Binary Object Representation (CBOR) data structures (RFC 7049). Its main goal is to provide an easy and unambiguous way to express structures for protocol messages and data formats that use CBOR or JSON.</t>
            </abstract>
          </front>
          <seriesInfo name="RFC" value="8610"/>
          <seriesInfo name="DOI" value="10.17487/RFC8610"/>
        </reference>
        <reference anchor="RFC8949" target="https://www.rfc-editor.org/info/rfc8949" quoteTitle="true" derivedAnchor="RFC8949">
          <front>
            <title>Concise Binary Object Representation (CBOR)</title>
            <author fullname="C. Bormann" initials="C." surname="Bormann"/>
            <author fullname="P. Hoffman" initials="P." surname="Hoffman"/>
            <date month="December" year="2020"/>
            <abstract>
              <t indent="0">The Concise Binary Object Representation (CBOR) is a data format whose design goals include the possibility of extremely small code size, fairly small message size, and extensibility without the need for version negotiation. These design goals make it different from earlier binary serializations such as ASN.1 and MessagePack.</t>
              <t indent="0">This document obsoletes RFC 7049, providing editorial improvements, new details, and errata fixes while keeping full compatibility with the interchange format of RFC 7049. It does not create a new version of the format.</t>
            </abstract>
          </front>
          <seriesInfo name="STD" value="94"/>
          <seriesInfo name="RFC" value="8949"/>
          <seriesInfo name="DOI" value="10.17487/RFC8949"/>
        </reference>
        <reference anchor="RFC9557" target="https://www.rfc-editor.org/info/rfc9557" quoteTitle="true" derivedAnchor="RFC9557">
          <front>
            <title>Date and Time on the Internet: Timestamps with Additional Information</title>
            <author fullname="U. Sharma" initials="U." surname="Sharma"/>
            <author fullname="C. Bormann" initials="C." surname="Bormann"/>
            <date month="April" year="2024"/>
            <abstract>
              <t indent="0">This document defines an extension to the timestamp format defined in RFC 3339 for representing additional information, including a time zone.</t>
              <t indent="0">It updates RFC 3339 in the specific interpretation of the local offset, which is no longer understood to "imply that UTC is the preferred reference point for the specified time".</t>
            </abstract>
          </front>
          <seriesInfo name="RFC" value="9557"/>
          <seriesInfo name="DOI" value="10.17487/RFC9557"/>
        </reference>
        <reference anchor="SI-SECOND" target="https://www.iso.org/standard/64974.html" quoteTitle="true" derivedAnchor="SI-SECOND">
          <front>
            <title>Quantities and units -- Part 3: Space and time</title>
            <author>
              <organization showOnFrontPage="true">ISO</organization>
            </author>
            <date month="October" year="2019"/>
          </front>
          <seriesInfo name="ISO" value="80000-3:2019"/>
        </reference>
        <reference anchor="TIME_T" target="http://pubs.opengroup.org/onlinepubs/9699919799/basedefs/V1_chap04.html#tag_04_16" quoteTitle="true" derivedAnchor="TIME_T">
          <front>
            <title>The Open Group Base Specifications Issue 7</title>
            <author>
              <organization showOnFrontPage="true">IEEE</organization>
            </author>
            <date year="2018"/>
          </front>
          <seriesInfo name="IEEE Std" value="1003.1-2017"/>
          <refcontent>Section 4.16 Seconds Since the Epoch</refcontent>
        </reference>
      </references>
      <references anchor="sec-informative-references" pn="section-9.2">
        <name slugifiedName="name-informative-references">Informative References</name>
        <reference anchor="C" target="https://www.iso.org/standard/74528.html" quoteTitle="true" derivedAnchor="C">
          <front>
            <title>Information technology -- Programming languages -- C</title>
            <author>
              <organization showOnFrontPage="true">ISO</organization>
            </author>
            <date month="June" year="2018"/>
          </front>
          <seriesInfo name="ISO/IEC" value="9899:2018"/>
          <annotation>Contents available via &lt;<eref target="https://www.open-std.org/jtc1/sc22/wg14/www/docs/n2310.pdf"/>&gt;</annotation>
          <refcontent>Fourth Edition</refcontent>
        </reference>
        <reference anchor="IEEE754" target="https://ieeexplore.ieee.org/document/8766229" quoteTitle="true" derivedAnchor="IEEE754">
          <front>
            <title>IEEE Standard for Floating-Point Arithmetic</title>
            <author>
              <organization showOnFrontPage="true">IEEE</organization>
            </author>
            <date month="July" year="2019"/>
          </front>
          <seriesInfo name="IEEE" value="754-2019"/>
          <seriesInfo name="DOI" value="10.1109/IEEESTD.2019.8766229"/>
        </reference>
        <reference anchor="ISO8601-2019" target="https://www.iso.org/standard/70907.html" quoteTitle="true" derivedAnchor="ISO8601-1:2019">
          <front>
            <title>Date and time -- Representations for information interchange -- Part 1: Basic rules</title>
            <author>
              <organization showOnFrontPage="true">ISO</organization>
            </author>
            <date month="February" year="2019"/>
          </front>
          <seriesInfo name="ISO" value="8601-1:2019"/>
        </reference>
        <reference anchor="ISO8601" target="https://www.iso.org/standard/15903.html" quoteTitle="true" derivedAnchor="ISO8601:1988">
          <front>
            <title>Data elements and interchange formats -- Information interchange -- Representation of dates and times</title>
            <author>
              <organization showOnFrontPage="true">ISO</organization>
            </author>
            <date month="June" year="1988"/>
          </front>
          <seriesInfo name="ISO" value="8601:1988"/>
          <annotation>Also available from &lt;<eref target="https://nvlpubs.nist.gov/nistpubs/Legacy/FIPS/fipspub4-1-1991.pdf">https://nvlpubs.nist.gov/nistpubs/Legacy/FIPS/fipspub4-1-1991.pdf</eref>&gt;.</annotation>
        </reference>
        <reference anchor="RFC3161" target="https://www.rfc-editor.org/info/rfc3161" quoteTitle="true" derivedAnchor="RFC3161">
          <front>
            <title>Internet X.509 Public Key Infrastructure Time-Stamp Protocol (TSP)</title>
            <author fullname="C. Adams" initials="C." surname="Adams"/>
            <author fullname="P. Cain" initials="P." surname="Cain"/>
            <author fullname="D. Pinkas" initials="D." surname="Pinkas"/>
            <author fullname="R. Zuccherato" initials="R." surname="Zuccherato"/>
            <date month="August" year="2001"/>
            <abstract>
              <t indent="0">This document describes the format of a request sent to a Time Stamping Authority (TSA) and of the response that is returned. It also establishes several security-relevant requirements for TSA operation, with regards to processing requests to generate responses. [STANDARDS-TRACK]</t>
            </abstract>
          </front>
          <seriesInfo name="RFC" value="3161"/>
          <seriesInfo name="DOI" value="10.17487/RFC3161"/>
        </reference>
        <reference anchor="RFC3339" target="https://www.rfc-editor.org/info/rfc3339" quoteTitle="true" derivedAnchor="RFC3339">
          <front>
            <title>Date and Time on the Internet: Timestamps</title>
            <author fullname="G. Klyne" initials="G." surname="Klyne"/>
            <author fullname="C. Newman" initials="C." surname="Newman"/>
            <date month="July" year="2002"/>
            <abstract>
              <t indent="0">This document defines a date and time format for use in Internet protocols that is a profile of the ISO 8601 standard for representation of dates and times using the Gregorian calendar.</t>
            </abstract>
          </front>
          <seriesInfo name="RFC" value="3339"/>
          <seriesInfo name="DOI" value="10.17487/RFC3339"/>
        </reference>
        <reference anchor="RFC5905" target="https://www.rfc-editor.org/info/rfc5905" quoteTitle="true" derivedAnchor="RFC5905">
          <front>
            <title>Network Time Protocol Version 4: Protocol and Algorithms Specification</title>
            <author fullname="D. Mills" initials="D." surname="Mills"/>
            <author fullname="J. Martin" initials="J." role="editor" surname="Martin"/>
            <author fullname="J. Burbank" initials="J." surname="Burbank"/>
            <author fullname="W. Kasch" initials="W." surname="Kasch"/>
            <date month="June" year="2010"/>
            <abstract>
              <t indent="0">The Network Time Protocol (NTP) is widely used to synchronize computer clocks in the Internet. This document describes NTP version 4 (NTPv4), which is backwards compatible with NTP version 3 (NTPv3), described in RFC 1305, as well as previous versions of the protocol. NTPv4 includes a modified protocol header to accommodate the Internet Protocol version 6 address family. NTPv4 includes fundamental improvements in the mitigation and discipline algorithms that extend the potential accuracy to the tens of microseconds with modern workstations and fast LANs. It includes a dynamic server discovery scheme, so that in many cases, specific server configuration is not required. It corrects certain errors in the NTPv3 design and implementation and includes an optional extension mechanism. [STANDARDS-TRACK]</t>
            </abstract>
          </front>
          <seriesInfo name="RFC" value="5905"/>
          <seriesInfo name="DOI" value="10.17487/RFC5905"/>
        </reference>
      </references>
    </references>
    <section anchor="collected-cddl" numbered="true" removeInRFC="false" toc="include" pn="section-appendix.a">
      <name slugifiedName="name-collected-cddl">Collected CDDL</name>
      <t indent="0" pn="section-appendix.a-1">This appendix collects the CDDL rules spread over the document into
one convenient place.</t>
      <figure anchor="fig-collected-cddl" align="left" suppress-title="false" pn="figure-6">
        <name slugifiedName="name-collected-cddl-rules-from-t">Collected CDDL Rules from This Specification</name>
        <sourcecode name="time-tag-collected-cddl.cddl" type="cddl" markers="false" pn="section-appendix.a-2.1">
Etime = #6.1001(etime-detailed)

etime-framework = {
  uint =&gt; any ; at least one base time
  * (nint/text) =&gt; any ; elective supplementary information
  * uint =&gt; any ; critical supplementary information
}

etime-detailed = ({
  $$ETIME-BASETIME
  ClockQuality-group
  * $$ETIME-ELECTIVE
  * $$ETIME-CRITICAL
  * ((nint/text) .feature "etime-elective-extension") =&gt; any
  * (uint .feature "etime-critical-extension") =&gt; any
}) .within etime-framework


$$ETIME-BASETIME //= (1: ~time)


$$ETIME-BASETIME //= (4: ~decfrac)
$$ETIME-BASETIME //= (5: ~bigfloat)


$$ETIME-ELECTIVE //= (-3: uint)
$$ETIME-ELECTIVE //= (-6: uint)
$$ETIME-ELECTIVE //= (-9: uint)
$$ETIME-ELECTIVE //= (-12: uint)
$$ETIME-ELECTIVE //= (-15: uint)
$$ETIME-ELECTIVE //= (-18: uint)


$$ETIME-ELECTIVE //= (-1 =&gt; $ETIME-TIMESCALE)
$$ETIME-ELECTIVE //= (-13 =&gt; $ETIME-TIMESCALE)
$$ETIME-CRITICAL //= (13 =&gt; $ETIME-TIMESCALE)

$ETIME-TIMESCALE /= &amp;(etime-utc: 0)
$ETIME-TIMESCALE /= &amp;(etime-tai: 1)


ClockQuality-group = (
  ? &amp;(ClockClass: -2) =&gt; uint .size 1 ; PTP/RFC8575
  ? &amp;(ClockAccuracy: -4) =&gt; uint .size 1 ; PTP/RFC8575
  ? &amp;(OffsetScaledLogVariance: -5) =&gt; uint .size 2 ; PTP/RFC8575
  ? &amp;(Uncertainty: -7) =&gt; ~time/~duration
  ? &amp;(Guarantee: -8) =&gt; ~time/~duration
)


$$ETIME-ELECTIVE //= (-10: time-zone-info)
$$ETIME-CRITICAL //= (10: time-zone-info)

time-zone-info = tstr .abnf
                 ("time-zone-name / time-numoffset" .det IXDTFtz)
IXDTFtz = '
   time-hour       = 2DIGIT  ; 00-23
   time-minute     = 2DIGIT  ; 00-59
   time-numoffset  = ("+" / "-") time-hour ":" time-minute

   time-zone-initial = ALPHA / "." / "_"
   time-zone-char    = time-zone-initial / DIGIT / "-" / "+"
   time-zone-part    = time-zone-initial *time-zone-char
                       ; but not "." or ".."
   time-zone-name    = time-zone-part *("/" time-zone-part)
   ALPHA             =  %x41-5A / %x61-7A   ; A-Z / a-z
   DIGIT             =  %x30-39 ; 0-9
' ; extracted from [RFC9557] and [RFC3339]


$$ETIME-ELECTIVE //= (-11: suffix-info-map)
$$ETIME-CRITICAL //= (11: suffix-info-map)

suffix-info-map = { * suffix-key =&gt; suffix-values }
suffix-key = tstr .abnf ("suffix-key" .det IXDTF)
suffix-values = one-or-more&lt;suffix-value&gt;
one-or-more&lt;T&gt; = T / [ 2* T ]
suffix-value = tstr .abnf ("suffix-value" .det IXDTF)

IXDTF = '
   key-initial       = lcalpha / "_"
   key-char          = key-initial / DIGIT / "-"
   suffix-key        = key-initial *key-char

   suffix-value      = 1*alphanum
   alphanum          = ALPHA / DIGIT
   lcalpha           =  %x61-7A
   ALPHA             =  %x41-5A / %x61-7A   ; A-Z / a-z
   DIGIT             =  %x30-39 ; 0-9
' ; extracted from [RFC9557]


Duration = #6.1002(etime-detailed)


simple-Period = #6.1003([
  start: ~Etime / null
  end: ~Etime / null
  ? duration: ~Duration
])


Period = #6.1003([
  (start: ~Etime,
   ((end: ~Etime) //
    (end: null,
     duration: ~Duration))) //
  (start: null,
   end: ~Etime,
   duration: ~Duration)
])


etime = #6.1001({* (int/tstr) =&gt; any})
duration = #6.1002({* (int/tstr) =&gt; any})
period = #6.1003([~etime/null, ~etime/null, ?~duration])
</sourcecode>
      </figure>
    </section>
    <section anchor="acknowledgements" numbered="false" removeInRFC="false" toc="include" pn="section-appendix.b">
      <name slugifiedName="name-acknowledgements">Acknowledgements</name>
      <t indent="0" pn="section-appendix.b-1">The authors would like to acknowledge the many comments from members
of the CBOR WG,
<contact fullname="Francesca Palombini"/> for her AD review,
<contact fullname="Thomas Fossati"/> and
<contact fullname="Qin Wu"/> for their directorate reviews, and <contact fullname="Rohan Mahy"/> for one more review late in the process.</t>
    </section>
    <section anchor="authors-addresses" numbered="false" removeInRFC="false" toc="include" pn="section-appendix.c">
      <name slugifiedName="name-authors-addresses">Authors' Addresses</name>
      <author fullname="Carsten Bormann" initials="C." surname="Bormann">
        <organization showOnFrontPage="true">Universität Bremen TZI</organization>
        <address>
          <postal>
            <street>Postfach 330440</street>
            <city>Bremen</city>
            <code>D-28359</code>
            <country>Germany</country>
          </postal>
          <phone>+49-421-218-63921</phone>
          <email>cabo@tzi.org</email>
        </address>
      </author>
      <author fullname="Ben Gamari" initials="B." surname="Gamari">
        <organization showOnFrontPage="true">Well-Typed</organization>
        <address>
          <postal>
            <street>117 Middle Rd.</street>
            <city>Portsmouth</city>
            <region>NH</region>
            <code>03801</code>
            <country>United States of America</country>
          </postal>
          <email>ben@well-typed.com</email>
        </address>
      </author>
      <author fullname="Henk Birkholz" initials="H." surname="Birkholz">
        <organization abbrev="Fraunhofer SIT" showOnFrontPage="true">Fraunhofer Institute for Secure Information Technology</organization>
        <address>
          <postal>
            <street>Rheinstrasse 75</street>
            <city>Darmstadt</city>
            <code>64295</code>
            <country>Germany</country>
          </postal>
          <email>henk.birkholz@ietf.contact</email>
        </address>
      </author>
    </section>
  </back>
</rfc>
