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We now have year 2010 but sometimes it still feels like living in the Stone Age of Computing. There's a smartphone, let's call it N97, with Symbian on it. Then there are a bunch of client computers such as a Debian workstation/homeserver running Sid, a Laptop running OS X with iCal and a Windows XP machine at work. Every machine itself (well, with the exception of the XP machine) is a nice piece of hard- and software offering a bunch of possibilities: you can manage your calendars, contacts and tasks.

The difficulty arise when you want to sync those calendars, contacts and tasks between all of the different machines.

There are several ways to address this task:

1. WebDAV:
   Setting up a WebDAV is no rocket science and you can easily sync your calendars easily with Sunbird or Thunderbird/Lightning for example. But that leaves the N97 ouf of syncing. The N97 can be synced with iSync on OS X, but iCal is not able to work on a single calendar. You can either export a calendar to a remote WebDAV or subscribe it. iCal ignores changes done in other clients and will overwrite those.
2. CalDAV 1:
   CalDAV (calendarserver) does require some more configuration before you can use it properly, but when done, it should be capable of syncing calendars, resources, tasks and such. Using CalDAV should work aorund the limitations of WebDAV as mentioned above. The calendars can be synced to CalDAV from iCal by creating a remote account and you can sync with iSync via Bluetooth. But you will need a local calendar in iCal, because you can't use iSync to sync your smartphone to your CalDAV remote calendar in iCal.
   iSync unable to use CalDAV for syncing

   Additionally there are problems when you delete an event from your CalDAV calendar on your smartphone. iSync will report an error like this:

   Freitag, 9. April 2010 21:45
   [Nokia N97]
   • Changes of „Events in writeprotected calendar“ on this phone are not permitted. These changes were ignored: test, 04/09/2010 23:00

   Deleting events in your local iCal calendar, however, is working well. In the end this result is not encouraging as I need the CalDAV calendars being in sync.
   Syncing with Sunbird on OS X doesn't work either. Maybe it would with DAViCal as server frontend?

3. CalDAV 2:
   Because syncing via iSync doesn't work as expected it would be a decent solution if the N97 could sync directly to CalDAV. Unfortunately it can't, although there seems some progress with Symbian there. If that is already integrated into v21.0.102 of N97 firmware, it would nice if someone could point me to how configure the N97 properly.
4. SyncML:
   Maybe another option would be to use some sort of SyncML server in order to sync calendars and stuff between those machines, but I don't know how OS X will work with that approach. Again, hints are welcome!

Syncing calendars and other stuff really seems to be painful. Using a third party webservice such as .Mac or Google Calendar is no option at all. I don't want to give private data out of my hands and control. So, a self hosted service is needed.
Dear lazyweb, is there a solution available for my problem? I hope so...