Many high-speed and night trains can already be reserved 3 months in advance, and will likely get fully booked sometime before its departure date (especially in busy travel seasons, such as summer and Christmas). All trains are generally bookable at least 2 months ahead of their scheduled departure. You can check the train pages for more information on specific train services.
We advise you to book seat reservations as soon as possible, especially during summer or the Christmas period! If a train is fully booked, use the planner in the app to find another train. To find alternatives that don’t require reservations, you can toggle on the option ‘No reservation needed’ in the planner. For more tips on how to avoid seat reservations, you can check out these articles.