1.5 Normative References reads in part:

• • • • • [dateTime] N. Freed, XML Schema Part 2: Datatypes Second Edition, http://www.w3.org/TR/xmlschema-2/#dateTime, W3C REC-xmlschema-2, October 2004.

That version has been superseded and the correct citation for the latest version reads:

• • • • • 
          XML Schema Part 2: Datatypes Second Edition, Paul V. Biron, A. Malhotra, Editors, W3C Recommendation, October 28, 2004, http://www.w3.org/TR/2004/REC-xmlschema-2-20041028/. Latest version available at http://www.w3.org/TR/xmlschema-2/.

Latest version should be a hyperlink.

BTW, I assume from the URL that you wanted to cite the current version for dateTime?

The correct way to do that is to have a label for the reference, here I would suggest XMLSCHEMA-2 and then in the text, when you need to invoke the W3C datatype say:

[XMLSCHEMA-2] 3.2.7 dateTime

that uses the normative reference in 1.5 and directs the reader to the appropriate section.