both dates (From and To) should be the same on update

Case:
admin can edit dates and change booked date to different one, but then end date should be validated and updated automatically according to the From date.

  //form_set_value($form[$fieldname][0]['#value']['value2'], array('date' => $date2, 'time' => $time1), $form_state); // set the same date of end event
  /* TODO */