The railplanner app works offline, the app get new timetables via updates. You have to look to apps or websites of the train carrier when you want to have up-to-date data. 

As @Angelo  explained there is no gurantee that the Railplanner is uptodate (Eurail aims it ofcourse) but sometimes changes on short notice aren´t loaded to the App :/

I recommend to use the local railplanner  or atleast Scotty (Austrian Rail) or DB Navigator (German Rail) as these get more updates and cover many European Countries Muj Vlak of Czech Rail is a  good offline app as Scotty & DB Navigator always need a data connection.

The baseline is: you cannot rely on the app, simply because it doesn't get enough updates. Do NOT use it to plan.