Make note of the following when importing iCal data.
Make sure the file you want to import contains correct iCal data.
How to import appointments or tasks in the iCal format:
Launch the Calendar or Tasks app.
Select the folder for importing appointments or tasks to in the folder tree.
Click the icon next to folder name. Click on .
Click on in the Import into window. Select a file in iCal format.
Click on .