Assigning current Time Stamp upon closure of defects

I assume you are using RTC as the defect provider.  RTC defects already have a "resolution date" attribute that does this.  If you've looked into this field already could you explain why it is insufficient?

In general the answer to your question is to edit the RTC project area process configuration via the Eclipse client:
1. Create a script based calculated value
2. Create a new timestamp attribute for the defect work item
3. Select the script created in step 1 in the "Calculated Value" dropdown of the new attribute
4. Configure the new attribute to have a dependency on the "Status" attribute. 
5. Add a read only presentation for your new attribute to the defect editor

This post contains a good sample script that manipulates dates.  Your script will need to be modified, for example to take the state of the workitem into account.

https://jazz.net/forum/questions/83120/how-to-show-the-difference-between-current-date-and-due-date-through-script-based-calculated-value

Just to have the complete script that works for me for "Reopen Date":
And to follow the same behavior like "resolution date" I make the field read only on the presentation.

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dojo.provide("com.example.ValueProvider");
dojo.require("com.ibm.team.workitem.api.common.WorkItemAttributes");
(function() {
    var WorkItemAttributes= com.ibm.team.workitem.api.common.WorkItemAttributes;
   
    dojo.declare("com.example.ValueProvider", null, {
        getValue: function(attribute, workItem, configuration) {
           
            var currentDate= new Date(); 
            if (workItem.getValue(WorkItemAttributes.STATE)=="6") {
                 return currentDate.getTime().toString();
            }
            return 0;                
        }
    });
})();
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Hi Joan,