function GetDays(ADate: TDate): Extended;
 var
  FirstOfYear: TDateTime;
 begin
  FirstOfYear := EncodeDate(StrToInt(FormatDateTime('yyyy', now)) - 1, 12, 31);
  Result := ADate - FirstOfYear;
 end;
 procedure TForm1.Button1Click(Sender: TObject);
 begin
  label1.Caption := 'Today is the ' + FloatToStr(GetDays(Date)) + '. day of the year';
 end;