Caldav calendars

The Caldav calendars at the Department of Mathematics

General information

At the Department Mathematik we have installed a Caldav server for general use. This is a web application with which several kinds of calendar programs can communicate. It serves calendars which can be integrated from many users in their personal calendars.

As a simple subscriber of our calendars you should be able to use different kinds of programs, because all of these should use the same (Caldav) interface for communicating with the server. Examples for such programs are: Thunderbird/Lightning, Evolution, AppleCalendar, Microsoft Outlook, …

In principle, also the modification of our calendars should work with any program that implements the Caldav protocol correctly. However, at the moment I can only say that changing our calendars should work with Thunderbird/Lightning and Evolution, because these two programs are freely available and run under Linux. Also Microsoft Outlook could be persuaded at least once, such that it could edit our calendars, you can find a preliminary short description about this below (which surely will have to be expanded). Also AppleCalendar could be configured for writing our calendars, however with some restrictions described below.

Information for users (especially of Thunderbird/Lightning)

Activating the calendar program Thunderbird/Lightning

Remark 1: If you already use some calendar program which is able to use network calendars, you can skip this section.

Remark 2: In the following we use the English language version of Thunderbird/Lightning.

You may install the calendar program Thunderbird/Lightning as follows:

  1. Make sure that Thunderbird is installed on your computer: Can you find the program in the menu? If not, ask your sysadmin to install it.
  2. Make sure that the Lightning-Add-on of Thunderbird is active. Via Menubar/Tools/Add-ons you can start the Add-on manager. Then you must select in the left column “Extensions”, whereupon you should see on the right side the Add-on “Lightning” which you can activate (if necessary) by pressing the button “Enable”.
  3. After a restart of Thunderbird you should see a new menu item “Events and Tasks”. There you can activate a menu item “Calendar”.
  4. You should then be shown a calendar. At the beginning this is a local calendar which is stored only on your computer or your account. Sometimes this is all you want, but in the following we want to subscribe also to network calendars. For this, the left column “Calendar” is important: Right-clicking in the lower empty region you can subscribe to such calendars.

Subscribing to a network calendar (in Thunderbird/Lightning)

  1. You enter the calendar view. Then a left column “Calendar” should be shown.
  2. You right-click in the empty lower region of that column. A menu should appear in which you can choose the menu point “New Calendar”. You will then be guided step-by-step through a series of input masks as explained in the following.
  3. In the first input mask you are asked if your calendar is located locally or in the network. We are interested in network calendars, so you choose “On the network”.

    Important: Personal calendars, which are NOT intended for public inspection should stay local on your computer! (Look also at Remarks 4 and 5 at the end of this document!)
  4. On the second input mask you are first asked which protocol the network calendar uses and second, with which URL the calendar server can be found (and third, if you want “Offline Support” – which I personally have always left active). We use “Caldav” (!), so you have to choose this option first. Then you enter the URL of the calendar which you want to subscribe. The URLs of our calendars generally have the following forms:
    1. If you only have read access:*/*/
    2. If you have (password-protected) write access:*/*/

    Important: In both cases the slash “/” at the end is important.

    In the following, we explain both forms in more detail:

    1. If you only have read access (which is the case, if your Idm-id is not registered for write access), please use an address of the following form*/*/
      Examples are:
    2. If you need to write certain network calendars, and if your Idm-id is registered for write access, you may use an address of the form*/*/
      instead, for example:

      When accessing that calendar, you are asked for your Idm and your password. (Note: Look also at Remark 1 below.)

  5. On the next mask you may choose a name for your new calendar as well as a color in which the events from this calendar are displayed. (The options “Show reminders” and “Email” I personally have always left as the are.)
  6. The next mask tells you that your calendar has been created. After acknowledging the name of the calendar should be shown in the left column and the dates of the new calendar should been shown in the calendar display on the right side.

Final remarks

  1. It is somewhat a problem that Thunderbird asks at every restart for an Idm-Login as soon as you subscribe to a calendar with write access. A remedy is to save the login data with Thunderbird. This is probably not an issue for most users. Nevertheless, it is a security problem to save such important passwords in programs as Thunderbird or Firefox. On the other hand, it is possible to shield the stored access data in Thunderbird with a master password, and I recommend to use this procedure.
  2. If you should have difficulties with subscribing to our calendars, please ask first colleagues of yours for help, who were already successful with subscribing some Department calendar. Ideally, you should even ask persons who use the same calendar program as yourself. Only if your colleagues can not give you advice, you should ask our system administrators or me (Nicolas Neuß).
  3. If you need new calendars (especially, new calendar groups or changes in the access rights for existing calendar groups), you may send me (Nicolas Neuß) an email, in which you ask for creating a calendar (group) for you. In this email you should tell me the name and the purpose for this calendar and also the names and Idm ids (not the passwords!) of all people who should have write access on the calendar.
  4. Personal calendars, which should not be seen by the public, should best be installed locally on your Computer! However, it can be useful also for network calendars, if only a special group of persons has read access. On special request we can also create such calendars (the public access with the http-address is simply dropped in this case).
  5. If you have the right to write some network calendar, please be careful that you enter your dates in the right calendar! Otherwise, embarrassing situations can easily appear. Probably the best way to avoid this, is if you switch on the read-only flag for all calendars (right-click on the calendar in the left column and choose “Properties” in the menu) and switch this flag off only temporarily for creation/change of calendar events.

Other calendar programs

Microsoft Outlook

Remark 1: Subscribing a network calendar for reading should be possible without problems. The following short description concerns especially the subscription with edit/write access.

Remark 2: For writing Caldav calendars, Outlook needs the extension caldavsync, which should be already installed on the Windows computers administered from our department computer team.

  • First, you have to create a new empty calendar in Outlook (which is not linked to
  • Then, in the caldavsync menu, one has to generate a profile as follows:
    • You choose with “Outlook Calendar” the newly created calendar.
    • You choose under “Caldav” our server with the https-path to the calendar (see above).
    • You enter Username/Passwd.
    • You switch on “Synch immediately” (“Sofort synchen”).
    • You switch “outlook server” to “mutual” (both directions).
  • After that you should test the installation by generating an entry in the new calendar and verify that the change has been passed to the server by accessing the calendar from another computer (don’t forget to synchronize the calendar manually there, because changes are usually propagated only with a delay). Additionally you can look in the caldavsync menu (menu point “Status”) when the last synchronization was done. Finally, you can delete your test entry and look again if this has worked as well


Subscribing for reading

Read subscription is easily possible by choosing within the menu “Ablage” the item “Neues Kalenderabonnement” and then entering the address of the calendar, for example The same procedure should also work with calendars which are not public. In this case the address has the form “…” and the access is authenticated with the FAU credentials.

Subscribing for read/write access

  • You choose in the menu “Ablage” the item “Account hinzufügen” and press the button “Anderen Caldav Account hinzufügen” in the list which appears.
  • A mask should appear where you set “Accounttyp” to be “Erweitert”. Then you can enter for username/password your FAU authentication (probably you can leave the password empty and will be asked if necessary). The “Serveradresse” has to be “” and the “Serverpfad” should be the full calendar path (e.g “/am3/calendar/”). The port should be set to 443, and also “SSL verwenden” has to be activated.
  • You should check your configuration by entering a test appointment. After that you should synchronize it with the server (choose in the menu “Darstellung” and then the item “Kalender Aktualisieren”).
  • Then you should check if your test appointment is visible on another computer with read access to this calendar (also there the calendar should be synchronized with the server first).
  • Finally, you should delete this test appointment, synchronize the calendar, and check on the other computer if the deletion succeeded.

Remark: AppleCalendar apparently cannot create different accounts with the same server address. Thus, it can access only one calendar on our server for read-write access. If you want to edit multiple calendars there, at the moment your only option is to use Thunderbird/Lightning. Maybe you should do this anyhow, because it is freely available and runs under many operating systems.