anchor.diff:  
   procedure TNullableTime.SetValue(AValue: TDateTime);
   begin
  +  InternalSetValue(AValue);
  +  FTagChanged:= false;
  +end;
  +
  +procedure TNullableTime.InternalSetValue(AValue: TDateTime);
  +begin
     FValue:= aValue;
     FIsNull := false;
   end;
  
positive.code:     FValue : String;
      function GetValue: String;
      procedure SetValue(AValue: String);
    public
      constructor Create(); override; overload;
      constructor Create(aValue: String); overload;
  
negative.code:       FValue : TDateTime;
        function GetValue : TDateTime;
        procedure SetValue (AValue : TDateTime);
        procedure InternalSetValue (AValue : TDateTime);
      public
        constructor Create(); override; overload;
        constructor Create(aValue: TDateTime); overload;
  