Bdtyktl

I am looking for a functional CalDAV client for Ubuntu, preferably open source. I was originally looking for one that works on 14.04, and now on 16.04.

Ubuntu 16.04

Following the advice of some commentators below, I gave another try to these programmes on Ubuntu 16.04. There are clear improvements, but it still is not possible to use a CalDAV calendar on Ubuntu.

Evolution

The most important hindrances to its usage on Ubuntu 14.04 have been fixed:

1. It now shows in the Lens.


2. It can be started with the "dummy" e-mail account.

Evolution comes with a good Help package that explains in detail the configuration of a CalDAV calendar. Although easy to set up, the CalDAV connection fails repeatedly and the calendar contents are never displayed. Naturally, it is neither possible to create new events. An error message is displayed that does not help much:

Unable to connect to 'Calendar': Cannot open calendar: Unexpected HTTP
status code 405 returned (Not Allowed) for URI:
https://account@my.owndrive.com/

Other programmes connect to the server with the exact same credentials, no clue why Evolution fails.

KOrganiser

Its problems have been fixed and now functions almost entirely. It is able to register my CalDAV account, fetch all my calendars and synchronise regularly. It even allows me to use my public SSH key instead of requiring my password.

However, Korganiser is programmed to work exclusively in the UTC time zone. I happen to live elsewhere, therefore all its functionality becomes useless when a new event created for 10h00 appears in all other devices at a different time...

Once more: are there any other functional alternatives to use and synchronise a CalDAV calendar on Ubuntu?

Previous tries on Ubuntu 14.04

These are the programmes from the Software Centre I tried so far, none of which functions on Ubuntu 14.04:

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  Evolution - it does not show in the Lens after being installed:

  
  
  

  

  
  


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  KOrganiser - displays an error message; the menus remain active but produce no results.

  
  
  

  

  
  


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  Calendar - displays a cryptic error message and exits.

  
  
  

  

  
  

What other clients exist out there?

I was experimenting with vdirsync + khal or with California, and have found that California syncs seamlessly with my Nextcloud caldav server. No email account necessary.

I had to add each calendar individually, it couldn't just discover them all via https://example.com/owncloud/remote.php/caldav but once I added each caldav link the calendars did sync.

I will note that it took hours for the first sync to happen, and I don't know what set it off. Then all of a sudden I got a password popup for each calendar and they're now synced. I've tested editing on Nextcloud and locally and the sync seems to be instantaneous.

I'd still like to know how to do this: Can I force calendar sync? but overall I'm pretty happy with it.

NOTE: Calfornia is totally unmaintained and after I filed 2-3 different bug reports someone finally told me that. I like California's week and agenda views, so I use it and Gnome Calendar, which has a sync button.

What about the Lighting add-on with Thunderbird? It works well with a NextCloud CalDAV server.

I finally managed to get Evolution working with my CalDAV service. This answer refers exclusively to version 3.18.5.2, with previous versions this procedure fails.

The trickiest bit is the e-mail configuration. You are forced to do so in order to use the calendar (go figure). Install Evolution from the Software Centre and start it up. A configuration menu appears; follow on with all options by default up to the Identify menu.

Enter your name and use the dummy address. If this address is not already there just use something like dummy@mail.com. Uncheck the Look up mail server... box, otherwise the process fails. Click Next.

In the Identity menu, you must choose the None option from the Server Type in order to follow on:

In the Sending Email menu select Sendmail as the Server Type and leave all other boxes empty or unchecked. Click Next on all the following menus to finish the configuration.

And finally you are using Evolution. If you are not shown the calendar press the Calendar button at the bottom left.

Now you must tell Evolution about your CalDAV service. Go to File > New > Calendar; the New Calendar dialogue appears. In the Type drop down select the CalDAV option. Then insert the URL address of your service, insert something like: https://my.owndrive.com/remote.php/caldav/. This is the URL for OwnDrive, it will be different for other services, you must know the exact address of your CalDAV service. Finally, insert your user name and click the Find Calendars button:

Wait for the remote calendars to be listed (it can take a little while). Select one of the calendars and click OK; click OK again in the New Calendar dialogue and repeat the process for other calendars.