Here's how to share iCal calendars among multiple users on a single Mac.
What you need to do is to move the iCal folder to a shared folder that is accessible to all users and then replace the iCal folder in each user's library folder with a "symbolic link' to the shared iCal folder. The symbolic link looks like an "alias", but if you try this using "aliases" to the shared iCal folder it will not work (trust me). You can create symbolic links using the Terminal, but I have no idea how, and the idea of using the Terminal scares me. The easiest way that I know of to create a symbolic link is with a shareware application called Cocktail. It allows you to do a number of different things including System Maintenance, Network Optimization, etc. It took me a while to remember how to do this; I originally found the information in the Discussions when iCal was first released, but apparently none of those original postings are listed in the forums anymore.
Here's how to do it (you must have Administrator privileges):
First locate your iCal folder (your user name > Library > Application Support > iCal) and make a copy of it (Finder > File > Duplicate). Drag the copy to your Desktop until you're sure iCal is being shared between users.
Next move the original iCal folder into a Shared folder in the Users folder (Hard Disk > Users > Shared > iCal). To make sure all users can access the information, select the Shared folder, choose File > Get Info, click the little Lock icon, then under "Ownership & Permissions -> Details" make sure that the "Owner" is "System", "Group" is "Wheel" and "Access" for Owner, Group and Others is "Read & Write". Do the same with the iCal folder within the Shared folder, but this time, under "Ownership & Permissions -> Details" make sure that the "Owner" is "your user name", "Group" is "Staff" and "Access" for Owner, Group and Others is "Read & Write" and click the "Apply to Enclosed Items" button. I basing this information on what the Ownership & Permissions are for each of the folders in my system.
Open Cocktail (I'm using version 3.6.5). Once the app is open (you must enter an administrator's user name and password) click on the "Files" button, then click on the "Links" button. Where it says "Create Symbolic Link" click on the "Choose" button. Navigate to the iCal folder (Hard Disk > Users > Shared > iCal) and click "Choose" again. In the "Save As" box that appears enter "iCal", then navigate to the Application Support folder in your Home folder (your user name > Library > Application Support) and click "Save". Quit Cocktail and open iCal. You should see all of your calendars as you did before.
Log in under each additional User, move that User's iCal folder (user name > Library > Application Support > iCal) onto the Desktop, then create another Symbolic Link to replace it, using Cocktail as described above. In each case you should see the same calendar information as when you were logged in under your user name. As a test, add a New Event or To Do in iCal under one user, log out and back in under another user and you should see the changes when you open iCal.
Once everything appears to be working, you can delete the iCal folders from each User's Desktop.
As an additional maintenance measure, use Disk Utility to repair Disk Permissions.
Unfortunately, if each User has his/her own calendars in iCal they will not be in the shared calendars. Only the calendars in the first iCal folder used to set up the shared folder will be available and I don't know of any way to merge or combine the other user's calendars into one.
Hope this helps and good luck!
