RTC:Script Based Calculated Value Set Timesatmp with now()

CLM 6.0.3 ifix5

I'm trying to set an timestamp attribute on save, which should get the date now.
1str try to ensure that it worked was to read from one attribute and writing in another:

dojo.provide("com.siemens.bt.workitems.providers.d1date");
dojo.require("dojo.date");
dojo.require("dojo.date.stamp"); dojo.require("com.ibm.team.workitem.api.common.WorkItemAttributes");

(function() {
var WorkItemAttributes=com.ibm.team.workitem.api.common.WorkItemAttributes;

dojo.declare("com.siemens.bt.workitems.providers.d1date", null, {
        getValue: function(attribute, workItem, configuration) {

          var mDate = workItem.getValue("com.siemens.bt.workitem.attributes.d3date");
          return mDate;   
 }});})();

This worked as expected :-)

2.try
                var today = new Date();
                var todayStr = dojo.date.stamp.toISOString(today, {milliseconds:true, zulu:true});
                result= todayStr;

3.try
                var datevar = workItem.getValue(WorkItemAttributes.MODIFIED);
                result= datevar ;
4.try 
                result="2017-06-26T13:50:07+00:00"

I do not find any way to write the actual date during save. And BTW I was not able to debug. Nor with debug=true nor console.log

Any help would be very welcome