/**
  * Set the start date value for all viewers but the emitting viewer.
  *
  * @param emitting emitting viewer
  * @param startDate value
  */
 private void setStartDate(TimeBarViewerInterface emitting, JaretDate startDate) {
   for (TimeBarViewerInterface viewer : _viewers) {
     if (!emitting.equals(viewer)) { // do not set on the emitting viewer
       viewer.removePropertyChangeListener(this);
       viewer.setStartDate(startDate.copy());
       viewer.addPropertyChangeListener(this);
     }
   }
 }