Hey

Every year at the second Sunday in december there is the european timetable change, where the new timetable for the next year starts. This year the new timetable starts at 12.12.2021.

Like for Germany, Switzerland and Austria the tamitable is online and you can use the timetable of the national carrier like bahn.de or fahrplan.oebb.at to look the new timetable. Like for Italy, you have to wait for some more weeks. 

on 12th December is the anual timetable change and they the most railcompanies just published their timetables this week on their own Websites. Eurail needs some time to load them in their own App.
Usually there are no big changes and you can plan with the timetable as before 12th December :)
another option is you use the websites of the Local Traincompanies.

Thanks for your replies. I was asking because my flight is for December 17, in that case, I will buy my eurail pass and wait till December 12 to make reservations. 
 

For some trains, making reservations for the new timetable is already possible and more and more trains will be added over the next few weeks.