Problem gelöst, danke an alle
Delphi-Quellcode:
function CurrentMonthFileName(const DestDir: string): string;
const MY_EXTENSION = 'txt';
begin
Result := Format('%s%s.%s',[IncludeTrailingPathDelimiter(DestDir),
FormatDateTime('yyyy-mm',Date),
MY_EXTENSION]);
end;
hats gebracht