hixie: Define whether the sign for UTC should be +00:00 or -00:00. (whatwg r4318)

hixie: Define whether the sign for UTC should be +00:00 or -00:00.
(whatwg r4318)

http://dev.w3.org/cvsweb/html5/spec/Overview.html?r1=1.3453&r2=1.3454&f=h
http://html5.org/tools/web-apps-tracker?from=4317&to=4318

===================================================================
RCS file: /sources/public/html5/spec/Overview.html,v
retrieving revision 1.3453
retrieving revision 1.3454
diff -u -d -r1.3453 -r1.3454
--- Overview.html	24 Oct 2009 22:44:54 -0000	1.3453
+++ Overview.html	24 Oct 2009 22:50:35 -0000	1.3454
@@ -3542,7 +3542,9 @@
   string</dfn> <var title="">datetime</var> is the <a href="#valid-global-date-and-time-string">valid global
   date and time string</a> representing <var title="">datetime</var> with the last character of the string not
   being a U+005A LATIN CAPITAL LETTER Z character (Z), even if the
-  time zone is UTC.</p>
+  time zone is UTC, and with a U+002D HYPHEN-MINUS character (-)
+  representing the sign of the time-zone offset when the time zone is
+  UTC.</p>
 
   <p>The rules to <dfn id="parse-a-global-date-and-time-string">parse a global date and time string</dfn> are
   as follows. This will return either a time in UTC, with associated