earlier hint, I explained how to combine two distinct calendars into one. But what if you’ve got more than two calendars you’d like to join together? Here’s a way to do just that.
First, create a new iCal calendar group (File -> New Calendar Group), and give it the name you’d like the new combined calendar to have.
Next, drag the calendars you’d like to combine into the new calendar group. Once you’ve dragged in all the calendars you’d like to combine, click once on the group to make sure it’s selected, then choose File -> Export as Calendar. (You’ll only see this menu option when you have a calendar group selected.) The filename and location don’t matter that much, because you’ll be deleting this file when you’re done with it.
Now choose File -> Import, and leave the radio button on the default Import an iCal File selection; then click Import. In the file selection dialog that appears, select the file you just exported, and click Import. When you do, one additional dialog will appear, letting you know that you’re adding new events. Click the drop-down menu, and choose New Calendar, at the very bottom of the list; then click OK.
At this point, your newly-combined calendar should import. You may see one more dialog warning you if you have any alarms set that open files or applications. Assuming you’ve created all your own calendars and alarms, then you can safely click the Keep All Alarms button. If you have any uncertainties, though, Remove Unsafe Alarms is the safe choice.
When the import finishes, you’ll have a new calendar in your sidebar, containing all of your combined events. Note that this technique—as well as the one covered in the previous hint—doesn’t perform a true merge, which would handle duplicate events across calendars. You’ll have to manually remove those yourself, using iCal’s search function.