Yesterday, Google announced that their calendar service (gCal) now supports the CalDAV protocol, allowing syncing with any calendar client that supports the standard.

They also released Calaboration, a Mac app to set up your gCal calendars in iCal. Unfortunately for Mac OS X 10.4 (Tiger) users, this only works in iCal 3.0 and higher, which only runs on Leopard.

The tools are great if you have been using gCal exclusively, and wish to use iCal on your Mac with it. If, however, like me, you have been using iCal and would like to utilise gCal to have your calendars on the go, there is no obvious way to switch them from local calendars to gCal-ready verisons, and the default interface in iCal doesn’t allow you to do so.

The solution is a little unintuitive but actually rather simple. Here’s how:

1. In iCal, select each of the calendars you’d like to sync in the sidebar, and, one by one, export them as an iCal file to the desktop by going to File -> Export and following the prompts. You can then quit iCal.

2. In your browser, log into your Google account and head over to the calendar. This will also work with a Google Apps for Your Domain Business account.

3. If you have more than one calendar you’d like to sync with iCal, create a new calendar in gCal for each one. For the moment, add g_ to the start of each one, and otherwise name them the same as your iCal calendars. You will be able to rename them in iCal once everything is synced.

4. Download Calaboration and fire it up.

5. Login to your account when prompted, and then select the calendars to create (you’ll probably want all of them).

6. Calaboration will do its thing, then prompt you to open up iCal again. You can now close Calaboration.

7. Back in iCal, Calaboration will have created a new calendar in iCal for each of your gCal calendars. They should be named the same as the ones created in gCal.

8. Select each of your newly created calendars in turn, select File -> Import and select the corresponding iCal file from your desktop that you exported earlier.

   This will import your calendar events and data into both iCal and gCal. Depending on how big your calendar is, how far back (and forward) it goes, and how quick your upload speed is, it could take a while. It took my general calendar about 15 minutes to sync. My birthdays calendar took less than 5.

9. Once you’ve completed each one, your calendars should all be nicely synced with gCal. Now it’s just a matter of going through and cleaning up. You can now delete the iCal calendars (listed under Calendars in the side bar) and rename the gCal calendars by removing the g_ we added earlier.

   Additionally, you can change the title of the sidebar sections by going into iCal preferences and changing the description for each account. At the moment it looks like a section is created for each calendar in your Google account. I assume this is a Google-side bug and will be fixed eventually.

(Google CalDAV features found via Daring Fireball)