Add rules for time values for all conforming documents.

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@@ -1929,12 +1929,13 @@ <h4>Representing Time</h4>
 <code>dateTimeStamp</code> construction first established by the [<a
 data-cite="XMLSCHEMA11-2#dateTimeStamp">XMLSCHEMA11-2</a>] specification. In
 order to reduce misinterpretations between different time zones, all time values
-SHOULD be specified in `dateTimeStamp` format, either in Universal Coordinated
-Time (UTC), denoted by a `Z` at the end of the value, or with a time zone offset
-relative to UTC. Time values that are incorrectly serialized without an offset
-MUST be interpreted as UTC. Examples of valid time zone offsets relative to UTC
-include `Z`, `+01:00`, `-08:00`, and `+14:00`. See the regular expression at the
-end of this section for a formal definition of all acceptable values.
+expressed in <a>conforming documents</a> SHOULD be specified in `dateTimeStamp`
+format, either in Universal Coordinated Time (UTC), denoted by a `Z` at the end
+of the value, or with a time zone offset relative to UTC. Time values that are
+incorrectly serialized without an offset MUST be interpreted as UTC. Examples of
+valid time zone offsets relative to UTC include `Z`, `+01:00`, `-08:00`, and
+`+14:00`. See the regular expression at the end of this section for a formal
+definition of all acceptable values.
         </p>
 
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