{ BrthDate: Date of birth }
function TFFuncs.CalcAge(brthdate: TDateTime): Integer;
var
 month, day, year, bmonth, bday, byear: word;
begin
 DecodeDate(BrthDate, byear, bmonth, bday);
 if bmonth = 0 then
  result := 0
 else
 begin
  DecodeDate(Date, year, month, day);
  result := year - byear;
  if (100 * month + day) < (100 * bmonth + bday) then
  result := result - 1;
 end;
end;

procedure TForm1.Button1Click(Sender: TObject);
var
 Month, Day, Year, CurrentMonth, CurrentDay, CurrentYear: word;
 Age: integer;
begin
 DecodeDate(DateTimePicker1.Date, Year, Month, Day);
 DecodeDate(Date, CurrentYear, CurrentMonth, CurrentDay);
 if (Year = CurrentYear) and (Month = CurrentMonth) and (Day = CurrentDay) then
  Age := 0
 else
 begin
  Age := CurrentYear - Year;
  if (Month > CurrentMonth) then
  dec(Age)
  else if Month = CurrentMonth then
  if (Day > CurrentDay) then
  dec(Age);
 end;
 Label1.Caption := IntToStr(Age);
end;

function CalculateAge(Birthday, CurrentDate: TDate): Integer;
var
 Month, Day, Year, CurrentYear, CurrentMonth, CurrentDay: Word;
begin
 DecodeDate(Birthday, Year, Month, Day);
 DecodeDate(CurrentDate, CurrentYear, CurrentMonth, CurrentDay);
 if (Year = CurrentYear) and (Month = CurrentMonth) and (Day = CurrentDay) then
 begin
  Result := 0;
 end
 else
 begin
  Result := CurrentYear - Year;
  if (Month > CurrentMonth) then
  Dec(Result)
  else
  begin
  if Month = CurrentMonth then
  if (Day > CurrentDay) then
  Dec(Result);
  end;
 end;
end;
procedure TForm1.Button1Click(Sender: TObject);
begin
 Label1.Caption := Format('Your age is %d',
  [CalculateAge(StrToDate('01.01.1903'), Date)]);
end;

DecodeDate(DM.Table.FieldByName('Born').AsDateTime, Year, Month, Day); // Дата рождения
DecodeDate(Date, YYYY, MM, DD); // Текущая дата
if (MM >= Month) and (DD >= Day) then
 Edit2.Text := IntToStr((YYYY - Year))
else
 Edit2.Text := IntToStr((YYYY - Year) - 1);