Hi,
Your need to point to the node associated with your Date Picker and convert the ISO8601 Date by scripting.
In JScript for example, it would be:
var date1 = XDocument.DOM.selectSingleNode( "//my:field1" ).text;
var dt1 = ISO8601ToDate(date1);
// dt1 can then be used as a regular date
function ISO8601ToDate(dateString)
{return new Date(dateString.split('-').reverse().join('/')) }
Hope that it helps.
Regards,
Franck Dauché