The new <time> element in HTML5  supports a range of different date/time/duration formats. Most of these match the value space of existing XML Schema datatypes (if not their lexical space), but there are two in particular that don't (at least these were the two that jumped out at me):
* timezone ('Z' or [+-]hh:mm)
* week (YYYY-Www)
It would ease extraction of data from HTML <time> elements if XML and RDF were able to support these datatypes. Could they be added (perhaps as xs:timezone and xs:gYearWeek)?
(See also http://lists.w3.org/Archives/Public/www-xml-schema-comments/2011OctDec/0025.html)
 http://www.whatwg.org/specs/web-apps/current-work/multipage/text-level-semantics.html#the-time-element (note this is not yet reflected in W3C version of the spec, but I think it's likely it will be)
MSM: so, our preference is that the note be published by the HTML5 WG.
...: and, our preference is that it won't be in the XML Schema NS, but if it becomes apparent that people really want it in our namespace then we'll consider it.
ACTION: MSM to get in touch with Jeni Tennison regarding production of a custom datatype given the parameters listed here in the minutes.
Resoved: mark bug as WORKSFORME after talking with Jeni.
The mail mentioned in comment 1 has now been sent , and as described there I'm marking this issue resolved. (I'm unilaterally changing the resolution from WORKSFORME to LATER, though, for reasons described in the mail.)