OXIO Headnote: date
Capture the date in the headnote in a metaDescribes element with a predicate of 'source-document-date'
Capture the date in ISO 8601 format.
<metaItem about="e">
<!-- content skipped for brevity -->
<metaDescribes predicate="product">OXIO</metaDescribes>
<metaDescribes predicate="publishing-group">Law-UK</metaDescribes>
<metaDescribes predicate="source-document-date">1973-06-28</metaDescribes>
<metaDescribes predicate="official-citation">UNJYB, 1973, p171</metaDescribes>
</metaItem>