Date Field update using SPServices?

In this below script,Date Field update using SPServices

 var dueDateVal = new Date().toISOString();
This is date format in Sharepoint
     $().SPServices({
        operation: "UpdateListItems",
        async: false,
        listName: "Paid Check",
         batchCmd: "Update",
         ID:id,
        valuepairs: [["Status","Completed"],["Completed_x0020_on",dueDateVal],["WF_Run",1]],
         completefunc: function(xData, Status) {
       
                         }
    });