I consider visiting Krakow and then moving to Vienna, Bratislava, Brno, or Prague.
Now, I would like to buy the cheapest train ticket from Krakow. But most European train websites such as GoEuro only show the list of tickets at the exact date, which you must fill in in advance.
I would rather like to buy the cheapest ticket possible, and don't mind the exact date that much. If possible, I would like to use a service such as Google Flights, that shows all dates and the cheapest ticket on each day. Something like the following:
Is there any such web service?