@Override
      public String calcLabel(ValueDescriptor descriptor, EvaluationContext evaluationContext, DescriptorLabelListener labelListener) {
        Value value = descriptor.getValue();
        if (value == null) {
          return "null";
        }
        else if (value instanceof LongValue) {
          return new Timestamp(((LongValue)value).longValue()).toString();
        }
        return null;
      }
@Override
      public String calcLabel(ValueDescriptor descriptor, EvaluationContext evaluationContext, DescriptorLabelListener labelListener)