Hi Alexander,

try this as well, this code will work irrespective of the date format

function onChange(control, oldValue, newValue, isLoading) {    

            if (isLoading || newValue == '') {    

                  return;    

            }    

            //Type appropriate comment here, and begin script below    

          var start_date = g_form.getValue('start_date');    

          var ga = new GlideAjax("calcDate"); //name of script include    

          ga.addParam("sysparm_name", "getDate"); //name of function in script include    

          ga.addParam("sysparm_start", start_date); //send start value to script    

          ga.addParam("sysparm_end", newValue);

          ga.getXML(checkDate); //callback function    

      }    

      function checkDate(response) {          

          var answer = response.responseXML.documentElement.getAttribute("answer"); //the response from the script    

          if (answer > 7) { //if the date received is more than 7 days from the start date    

          alert("End date cannot be later than 7 days after start date.");    

          g_form.setValue('end_date', ''); //remove value from end date field    

          return false;    

          }    

      }

script include code-

var calcDate = Class.create();      

      calcDate.prototype = Object.extendsObject(AbstractAjaxProcessor,{      

          getDate : function() {      

              var startDT = new GlideDate();

              startDT.setDisplayValue(this.getParameter('sysparm_start'));

              var endDT = new GlideDate();

              endDT.setDisplayValue(this.getParameter('sysparm_end'));

              var duration = new GlideDuration();

              duration= GlideDate.subtract(startDT, endDT);

              return duration.getDayPart();  

          },      

          type: 'calcDate'      

      });  

Regards,

Lavanya