Preferences -> Logging -> Archiving -> Tick 'Create a directory each month for every file'?
Asetukset -> Lokitiedostot -> Arkistointi -> Tick 'Luo kansio kuukausittain tiedostoille'?
I've understood that you're finnish, so i added finnish way also.
Anyway, that should do it. I have ticked that and it's working. Also it's translated into estonian as it would create every month a new folder to all log files.
By the way, that topic doesn't exist anymore.