How far in advance can I buy the group saver fare europe?

You can book online from up to 6 months in advance until shortly before departure (up to 12 months in advance for Belgium, Netherlands, Luxembourg and Switzerland).
You can book up to 12 months in advance until shortly before departure at the DB Travel Centre, DB agency or by telephone.

If the travel information does not show any connections, the date you selected is outside the current timetable period. The next timetable is usually released in mid-October, You can book your tickets after the release.