The daytrains (Intercity´s) from Hamburg to Copenhagen can´t be reserved via bahn.de :/
It´s quite easy possible via b-Europes webpage of DSB Udland for the Nighttrains of SJ or Snälltoget you have to use their own websites

Thank you, seewulf.

But even on this website it is not possible booking for 30.6 or later

Trains are still NOT planes-what anyone takes for granted in the skies=book more as 1 yr advance is for trains an utmost rarity. Tipical IR-newbees seem to think they have nowadays to settle anything (and even also book hostels etc) half years advance=total nonsense.

In fact you can always go without any cumbersome advance by using local domestic DSB IC toget till last stop before DE border (Padborg), then use local trains further on, via Flensburg (where the germans have their office that registrates the points one gets for traffic offenses). Takes a little longer, more changes to worry about, Unless you are determined to use that overnight train that only runs summer season.

Its the curse of these planners over longer distance that anyone looks at and that present only direct trains-just cut up in segments.

@mcadv sorry i was a little bit worried because the Tour de France Start will be in Kopenhage and I thought all trains are already occupied  ;)

I can book Hamburg - Copenhagen for 30 June of even later:

So what did you try? Anyway, it's still a long time into the future.