如何知道某个日期是某年的第几天

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;