Philipp's Developer Notes: Using CalDAV with Google Calendar
When I arrived at the Mozilla Firefox+ Summit 2008 on the 28th, I was surprised to hear, that Google announced the release of CalDAV support for Google Calendar while I was up in the air. At first I thought Simon was joking when he told me, but he was not!
I had very mixed feelings on this step. On one side this is a really great step. Supporting CalDAV means that more applications will be able to natively read and write to Google Calendar, without the need for third party applications that proxy the write process through the web-based API. In the long run this means less work for me since at some point the Provider for Google Calendar will not be needed anymore. Instead of fixing the Provider for Google Calendar, I can focus on CalDAV bugs, which benefits both Google users and those of other servers. Also this is something I've been hoping for a while now and have asked Google employees about in the past.
On the other side, I was of course a bit disappointed, that all the work and pain I've put into the Provider for Google Calendar is now being made obsolete. This didn't last long though, since thats just the way it goes with software and I was always aware that at some point something like this would happen. Nevertheless I have no regrets since I think I've done a great deal for users of the Provider and the feedback I've gotten was overwhelming (and mostly positive). Writing the Provider also taught me a great deal about the Mozilla codebase and how the calendar application works, so it was definitely worth it!
Since the above sounds much like I'm going to drop work on the Provider right away and suggest to use CalDAV, let me tell you that it is quite the contrary. As noted in Google's blog post, the release of CalDAV support is developer-focused. There are a number of known issues and application support is currently quite minimal. At the time of release, as far as I know only Apple iCal actually works. Therefore, I'd still suggest to use the Provider for Google Calendar until Google's CalDAV server is more mature.
Using a few workarounds introduced in bug 448561 and bug 451455 I was able to make Sunbird/Lightning's CalDAV work with Google. If you are interested in testing, please feel free to take a look at the latest nightlies (Sunbird / Lightning).