Calendar Options for Linux Users
Since the shutdown of the "Corporate Time" (CTime) calendar tool some years ago, no DESY wide solution for a work calendar for Linux users has come up (although there is talk about a future solution, but it is unclear when this will appear).
The only official calendar is the one from Microsoft Exchange, which you can access from Linux either via the web front-end webmail.desy.de or using the Windows Terminal Server via Outlook. Since both options are not perfect (think of not-working reminder pop-ups), many Linux users use a private calendar, which has the disadvantage of not having the possibility to share events. Further, it is not visible by other group members and the calendar is not being accessible from the outside.
Note: Using a Google calendar for work data is probably critical with respect to legal matters, since the data is stored somewhere in the U.S.
Setting up Lightning
Lightning is an add-on for the Thunderbird mail client. You can download it via the official file server. Note: the version offered on the home page does not work with the version 2 of Thunderbird which is pre-installed in Scientific Linux 5 versions at DESY. You can use the links here to download the 0.9 version of Lightning which still works with Thunderbird 2: 32bit machine 64bit machine
The add-on is installed in Thunderbird as usual: go to Tools → Add-Ons → Install (at bottom of newly opened window) → choose the downloaded file and install it. The usage of Lightning should be pretty straight forward, some help can be found in the FAQ. Now you can easily create local (=private) calendars on your hard disk.
Tip: If you do not want to switch between the mail and the calendar view in Thunderbird: open one of your mail folders (right click → open) in a new window and choose in this window the calendar view. Unfortunately, Thunderbird doesn't remember this layout after a restart.
Tip: A file containing the dates of german holidays from 2010-2015 can be found here; this you can import in Lightning.
Connecting to the Exchange server
For the setup that is currently used at DESY (Exchange Server 2003 and Thunderbird 2), there seems to be only one solution to connect the two. This is using DavMail as a local gateway server.
DavMail is a Java program that starts a local server which can read from the Exchange web front-end and offers a CalDav port to Lightning. You can download it here (under "Linux (other)"). The installation is described here. You can start the DavMail server by running davmail.sh (for daily use it is probably convenient to create a shortcut on your desktop or add it to the autostart). At the first start a setup menu should appear. How to set it up is described here. Since only the CalDav gateway is interesting in the DESY setup, all others should be un-ticked. For the OWA (Exchange) URL enter https://owa.desy.de/exchange/. The settings are shown in the screenshot below:
After a successful start, a symbol should appear in your system tray.
Since the DavMail server is only running locally and per default not open to access from other machines, security impact should be negligible.
Settings in Lightning
To connect to your exchange calendar, create a new calendar in Lightning (right click on a free spot in the list of your calendars in the calendar view and choose "New Calendar"). Choose "On the Network" and then "CalDaV". Location is of the form:
Replace here "email@example.com" with your official firstname.lastname@example.org email address. Any addition to the URL above like e.g. "/test" would refer to a sub-calendar. On the next tab, you can assign a nickname to this calendar . Login data would be "WIN/yourusername" and your normal password.
Now everything should be working. Events entered via Lightning should appear under Outlook and vice versa. For detailed settings (e.g. privacy settings) of your Exchange calendar, you might still have to use the Windows Terminal Server and do them in Outlook, but everyday work with adding/modifying/deleting events works from Lightning.
Tip: If you had an existing local Lightning calendar, you can import it to the Exchange calendar. For this, you first export it (right-click on the calendar in Lightning → "Export Calendar"). Make sure to give the file the ending .ics. Then you can import it again by choosing "Import Calendar" in the "File" menu and choose your Exchange calendar to import into (Note: the import may take some minutes, depending on how full your existing calendar was).