I found a solution by myself: MS-Outlook!
For those who are interested:
- the Kopano Outlook Addin have to be installed and working.
- Setup a Kopano-Account in Outlook with the old kopano calendar which should be copied.
- When the Account is running go to Calender and change to listview
- copy all entries or the entries you want, to your local outlook calendar (it is the best when this local outlook-calender is a empty one!!!)
- when the copying is done delete the account in outlook an setup the new kopano-account on the new or other kopano-server. Go to the new outlook-calendar (listview) and copy the local outlook-calendar to the kopano-calendar.
Note: i have integrated the the public holidays by outlook menu before so now they are in kopano-calendar as well!
This is surely no enterprise-solution because you have this process to do for all kopano-accounts you want to be copied.