i used the below script , its working good

var timeInStart = current.u_on_call_start;

  var dateTimeStart = timeInStart.split('T');

  var dateStart = dateTimeStart[0];

  var timeStart = dateTimeStart[1].split('Z');

  t =   dateStart + " " + timeStart[0];

  var start = new GlideDateTime(t);

      var plannedStartDt = new GlideDateTime(start);

              z =   plannedStartDt; * converted Local Date Time *