A couple weeks ago, I got an email saying my train from Munich to Vienna was cancelled. But then a few days ago, I saw that the train number I already booked is now a train to Vienna but it is about 40 min earlier than originally booked. Do I have to take that same train number that is earlier, or am I able to take a later train since my original train was cancelled?
If ticket was booked via Deutsche Bahn I recommend to ask DB directly by Help & Contact for this detailed and very special question.
A forum can only give opinions and single trip experiences, no answers you can rely on contract-wise.
You are free to use any other train on that day, even if you have a saver fare ticket. If you have paid for a seat reservation, go to the Reieezentrum in Munich Hbf and ask for a refund or an exchange.
BTW, this is not an "opinion", but the current regulation, which you can study in detail here:
https://int.bahn.de/en/booking-information/passenger-rights/legal-regulations
I do not see this case covered in the link when a train is now driving again but earlier.
You refer to the regular train cancellation; I am not 100% sure that this is the valid case here.
If DB cancelled the train you can take your ticket to the information DB counter and they will adjust it for you.
Unfortunately, I don't have time to search for the corresponding English text at the moment, but the case is covered by the text quoted below (original in German). I'm receiving emails like this all the time, even when a train leaves just a few minutes early. Incidentally, this is not a voluntary gesture of goodwill on the part of Deutsche Bahn, but is the result of an order issued by the Federal Railway Authority.
[quote]
"Was kann ich tun, wenn ich eine Benachrichtigung zu meiner Reise bekomme?
Sie haben eine Benachrichtigung erhalten, weil Ihr gebuchter Zug nicht mehr im aktuellen Fahrplan gefunden wurde. Das heißt, dass Ihr Zug z.B. wegen einer Baustelle oder einem unvorhersehbaren Ereignis nicht wie ursprünglich geplant fährt. So kann er zu einer anderen Zeit oder von einem anderen Bahnhof aus fahren oder ganz ausfallen.
Was kann ich in diesem Fall tun?
Suchen Sie in der Reiseauskunft am gewünschten Tag nach einer Alternative. Den Link dazu finden Sie direkt in der Benachrichtigungs-Mail. "
[/quote]
(What can I do if I receive a notification about my journey?
You have received a notification because your booked train can no longer be found in the current timetable. This means, for example, that your train is not running as originally planned due to roadworks or an unforeseen event. It may run at a different time or from a different station or be canceled altogether.
What can I do in this case?
Search for an alternative in the journey planner on the desired day. You will find the link directly in the notification e-mail.)
If DB cancelled the train you can take your ticket to the information
DB counter and they will adjust it for you.
No, you do not need to have your ticket adjusted. In Germany tickets are for a route, not a train. So if the train you selected during booking disappears you just taken another train, and you are supposed to just look this up yourself.
If you have a discounted train ticket with "zugbindung" that gets lifted the moment the schedule changes.