anchor.diff:  procedure TNullableTime.SetValue(AValue: TDateTime);
   begin
     InternalSetValue(AValue);
  -  FTagChanged:= false;
  +  SetTagChanged(false);
   end;
   
   procedure TNullableTime.InternalSetValue(AValue: TDateTime);
   begin
     FValue:= aValue;
  -  FIsNull := false;
  +  SetIsNull(false);
   end;
   
   constructor TNullableTime.Create();
  
positive.code:     function CheckIfDifferentAndAssign(const aValue : Variant) : boolean; override;
      function AsVariant: Variant; override;
      procedure Trim();
      procedure ChangeToBlankIfNull;
      function IsEqual (const aValue : String) : boolean;
      function IsEqualCaseInsensitive (const aValue : String): boolean;
  
negative.code:     function CheckIfDifferentAndAssign(const aValue : Variant) : boolean; virtual; abstract;
      function AsString: String; virtual; abstract;
  
      property IsNull: Boolean read GetIsNull write SetIsNull;
      property NotNull: Boolean read GetNotNull;
      property TagChanged: Boolean read GetTagChanged;
    end;
  
    { TNullablesList }
  