Update "datetime" documentation in Definitions.xid.xml

@@ -113,13 +113,13 @@
         <type name="float16" size="4">
         <type name="float16" size="4">
             <comment>32-bit, IEEE 754 binary16</comment>
             <comment>32-bit, IEEE 754 binary16</comment>
             <comment>C/cpp usually a "float"</comment>
             <comment>C/cpp usually a "float"</comment>
-            <artifact>https://en.wikipedia.org/wiki/Half-precision_floating-point_format</artifact>
+            <artifact>https://wikipedia.org/wiki/Half-precision_floating-point_format</artifact>
         </type>
         </type>
         -->
         -->
 
 
         <type name="float32" size="4">
         <type name="float32" size="4">
             <comment>32-bit, IEEE 754 binary32</comment>
             <comment>32-bit, IEEE 754 binary32</comment>
-            <artifact>https://en.wikipedia.org/wiki/Single-precision_floating-point_format</artifact>
+            <artifact>https://wikipedia.org/wiki/Single-precision_floating-point_format</artifact>
             <lang name="c" type="float"/>
             <lang name="c" type="float"/>
             <lang name="cpp" type="float"/>
             <lang name="cpp" type="float"/>
             <lang name="java" type="XidFloat" include="com.comtechtel.tensor.xid.XidFloat"/>
             <lang name="java" type="XidFloat" include="com.comtechtel.tensor.xid.XidFloat"/>
@@ -127,7 +127,7 @@
         </type>
         </type>
         <type name="float64" size="8">
         <type name="float64" size="8">
             <comment>64-bit, IEEE 754 binary64</comment>
             <comment>64-bit, IEEE 754 binary64</comment>
-            <artifact>https://en.wikipedia.org/wiki/Double-precision_floating-point_format</artifact>
+            <artifact>https://wikipedia.org/wiki/Double-precision_floating-point_format</artifact>
             <lang name="c" type="double"/>
             <lang name="c" type="double"/>
             <lang name="cpp" type="double"/>
             <lang name="cpp" type="double"/>
             <lang name="java" type="XidDouble" include="com.comtechtel.tensor.xid.XidDouble"/>
             <lang name="java" type="XidDouble" include="com.comtechtel.tensor.xid.XidDouble"/>
@@ -136,7 +136,7 @@
         <!--
         <!--
         <type name="float128" size="8">
         <type name="float128" size="8">
             <comment>128-bit, IEEE 754 binary128</comment>
             <comment>128-bit, IEEE 754 binary128</comment>
-            <artifact>https://en.wikipedia.org/wiki/Quadruple-precision_floating-point_format</artifact>
+            <artifact>https://wikipedia.org/wiki/Quadruple-precision_floating-point_format</artifact>
             <lang name="cpp" type="long double"/>
             <lang name="cpp" type="long double"/>
         </type>
         </type>
         -->
         -->
@@ -166,7 +166,12 @@
         </type>
         </type>
 
 
         <type name="datetime" size="8">
         <type name="datetime" size="8">
-            <comment>nanoseconds since Jan 1, 1970.</comment>
+            <comment>
+                nanoseconds since Jan 1, 1970 UTC.
+                ISO-8601 for string formats (e.g. JSON).
+            </comment>
+            <artifact>https://www.iso.org/standard/40874.html</artifact>
+            <articact>https://wikipedia.org/wiki/ISO_8601</articact>
             <lang name="c" type="uint64_t" include="stdint.h"/>
             <lang name="c" type="uint64_t" include="stdint.h"/>
             <lang name="cpp" type="::Tensor::Types::DateTime" include="Tensor/Types/DateTime.h"/>
             <lang name="cpp" type="::Tensor::Types::DateTime" include="Tensor/Types/DateTime.h"/>
             <lang name="java" type="XidDateTime" include="com.comtechtel.tensor.xid.XidDateTime"/>
             <lang name="java" type="XidDateTime" include="com.comtechtel.tensor.xid.XidDateTime"/>
@@ -174,7 +179,8 @@
         </type>
         </type>
 
 
         <type name="UUID" size="16">
         <type name="UUID" size="16">
-            <comment>16 byte UUID</comment>
+            <comment>16 byte UUID.</comment>
+            <artifact>https://wikipedia.org/wiki/Universally_unique_identifier</artifact>
             <lang name="c" type="UUID" include="Tensor/CXMF/uuid.h"/>
             <lang name="c" type="UUID" include="Tensor/CXMF/uuid.h"/>
             <lang name="cpp" type="::Tensor::Types::UUID" include="Tensor/Types/uuid.h"/>
             <lang name="cpp" type="::Tensor::Types::UUID" include="Tensor/Types/uuid.h"/>
             <lang name="java" type="XidUuid" include="com.comtechtel.tensor.xid.XidUuid"/>
             <lang name="java" type="XidUuid" include="com.comtechtel.tensor.xid.XidUuid"/>