Docs: Fixed day/year format in QDateTime

QDateTime takes dd and yyyy. It is confusing when the example format strings don't work because they use DD YYYY, and it is a silent error with the characters not getting substituted and can be easy to miss.

It is less clear how to fixup the qnamespace.qdoc problem.

\c{YYYY-MM-DDTHH:mm:ssTZD} (e.g., 1997-07-16T19:20:30+01:00)

Is this okay?
\c{yyyy-MM-ddTHH:mm:sst} (e.g., 1997-07-16T19:20:30UTC)

But isn't the cited ISO 8601 require it to be the +/-HH:mm format?  I don't see a character to output that for in QDateTime.