Claculer l’age entre deux date

1.  Interface :

Dans une fiche  placer :

Deux boutons un pour caption 'calculer' et  l'autre fermer.

trois label: un pour caption : 'Du' autre ' Au' autre ' Age'.

2. Programmation : 

déclarer ces deux fonction :

function Nomberofdays(const DT1, DT2: TDateTime): LongInt;

begin

   Result := Trunc (DT2) - Trunc (DT1);

End;

 function Diffa(const DT1: TDateTime; const DT2: TDateTime):string ;

var  Day1, Month1, Year1 ,Day2, Month2, Year2,IDay,IMonth,IYear: word;

begin

IYear:=0;

 DecodeDate(dt1,Year1,Month1,Day1);

 DecodeDate(dt2,Year2,Month2,Day2);

       if Year2>= Year1 then IYear := Year2 - Year1 else

           begin

           showmessage('Inversé les Dates SVP');

           abort;

           end;

      if  Month2>= Month1          then
              IMonth := Month2 - Month1 
else

            begin

               IMonth := 12 + Month2 - Month1 ;

               IYear  := IYear -1 ;

               if IYear =65535 then   //-1

                begin

                showmessage('Inversé les Dates SVP');

                abort;

                end;

            end;

       if  Day2>= Day1          then
           IDay := Day2 - Day1 else

           begin

             IDay := 30 + Day2 - Day1;

             IMonth :=  IMonth -1;

             if IMonth =65535 then

                begin

                IMonth := IMonth +12;

                IYear :=  IYear -1;

                   if  IYear = 65535  then

                     begin

                     showmessage('Inversé les Dates SVP');

                     abort;

                     end;(* *)

                  end;

           end;

Double clique sur le bouton "Claculer"  écrire :

procedure TForm1.Button2Click(Sender: TObject);

begin

 label3.Caption:=diffa(dt1.date,dt2.Date);

end;