The Living Thing / Notebooks :

Calendars and contact databases, digital, networked

Usefulness: 🔧
Novelty: 💡
Uncertainty: 🤪 🤪
Incompleteness: 🚧 🚧 🚧

Google calendar, iCloud etc exist. But who wants to gift Google/Apple with free information about all their friends? Well, most of my friends, TBH. But it leaves me feeling gross.

There are two problems with event scheduling to solve:

  1. The technical end of getting calendars and reminders on your phone and desktop machine
  2. The social problem of discovering and coordinating events with your contacts

That’s the raw logistical end; there is also the question of social event discovery. What is the social platform that allows us to collectively discover events? Facebook has made a bid to be a monopoly provider of these services, about which I feel negative.

Jargon to know here: CalDAV and CardDAV are the de facto standards to sync your calendar and contact information in a machine readable form respectively. All you need is a server which talks those standards and you can use whatever calendar client you’d like. In principle, this is all you need to get your smartphone telling you to leave your house now to get to dinner with your grandmother.

Another useful keyword here is “groupware” which AFAICT is a buzzword left over from the mid 2000s which meant “calendars+contacts+email+other shit that turned out to be less wise to integrate” and now means “calendars+contacts+email”.

So! Running your own. that’s a legitimate use of your precious free time, right? Uh.

GUI Calendar clients


GNOME mail client Evolution supports icloud interoperation and other CardDAV servers. Possibly so do other CardDAV options. There is an iOS app Contact mover which brute-force synchronises icloud contacts to CardDAV servers. I’m not a massive fan because it leaks memory and uses astonishing amounts of CPU to do the contact syncing. You can hear my CPU fan across the room and watch the battery meter drop every hour on the hour while this damned thing is installed. It seems to be pretty much the only Linux app that has seamless CardDAV support natively.


Thunderbird gets CardDAV support, I think, via a plugin, SOGo Connector, which comes bundled with the calendar extension lightning? Confusingly there is also Sogo integrator, which targets their groupware server specifically:

First of all, the SOGo Connector extension transforms Thunderbird into a full DAV client for groupware servers such as SOGo, eGroupware or Citadel. It does this by adding support for remote DAV address books and by adding features to be used along with the Lightning calendar extension. …

On the other hand, the SOGo Integrator extension transforms Thunderbird into a pure “heavy” client for SOGo. Whereas the SOGo Connector is meant for portability (horizontal integration), the SOGo Integrator makes use of the features and layout only available from SOGo (vertical integration).

It is not immediately obvious how to configure it, but it is not so hard; one simply needs the CalDAV URL.


Syncevolution is a full contact-syncing app which supports various CardDAV implementations with some restrictions.


Mulberry is a defunct open source client for calddav and carddav and mail.

Calendar client code libraries

You want to do something really geeky with your caldav and some server. OK.

Calendar servers

The only contact syncing that works well with macOS is icloud (they claim to support any CardDAV server, but in practice I have had glitches and failures with all other servers that I have tried.


iCloud setup for non-apple clients requires a few steps

Log in to!&page=signin to set up an app password. Then you can use that password plus the usual icloud username to work with other clients. As we learn from the Blackberry docs, CardDAV URL is and contacts URL is



Apple Calendar Server

Apple’s open-source Calendar Server. Does contacts too. I don’t think that Apple any longer dogfoods this particular bit of software, but it might work OK. Also it’s bloated. macOS/Windows/Linux: Radicale seems to be less bloated than the Apple thingy.


Radicale is a small but powerful CalDAV (calendars, todo-lists) and CardDAV (contacts) server, that:



Ever wanted to get rid of Outlook? DavMail is a POP/IMAP/SMTP/CalDAV/CardDAV/LDAP exchange gateway allowing users to use any mail/calendar client (e.g. Thunderbird with Lightning or Apple iCal) with an Exchange server, even from the internet or behind a firewall through Outlook Web Access.

DavMail also supports the CardDAV protocol to sync address books. This new feature is sponsored by French Defense / DGA through project Trustedbird.[…]

DavMail gateway is implemented in java and should run on any platform. Releases are tested on Windows, Linux (Ubuntu) and Mac macOS. Tested successfully with the Iphone (gateway running on a server).

Nextcloud calendar plugin

nextcloud, the file sync server, also optionally supports CardDAV and a Calendar GUI.


kolab is the open-source backend of, e.g., kolabnow and used by such apps as kube.



SOGo is a fully supported and trusted groupware server with a focus on scalability and open standards. SOGo is released under the GNU GPL/LGPL v2 and above.

SOGo provides a rich AJAX-based Web interface and supports multiple native clients through the use of standard protocols such as CalDAV, CardDAV and GroupDAV, as well as Microsoft ActiveSync.

SOGo is the missing component of your infrastructure; it sits in the middle of your servers to offer your users a uniform and complete interface to access their information. It has been deployed in production environments where thousands of users are involved.


iRedMail is a packaged system for some of these projects

With iRedMail, you can deploy an OPEN SOURCE, FULLY FLEDGED, FULL-FEATURED mail server in several minutes, for free.

We did the heavy lifting of putting all the open source components together and applying best practices. Our product does all the major tasks for you. Furthermore we offer professional support to back you up in case you have some problems.[…] Manage your calendars (CalDAV), address books (CardDAV), tasks on a easy to use web UI or your mobile devices (iOS, Android, BlackBerry 10, Windows Phone).

In particular the calendar/contacts server comes from sogo.

Social event discovery

This one is the real weak spot. Facebook has an effective monopoly on this in the west.

Calgator is an open source community calendar platform written in Ruby on Rails that runs, a Portland tech calendar.

Gigtripper looks interesting.