One of the difficulties of creating multiple calendars in iCal is working out how many you actually need. Do you create a "College" calendar and a "Homework" calendar, or should you make just one for all you college activities?

If you start off with two separate calendars it is fairly easy to merge them into one if you later decide to. Luckily you don't need to go through every single event and change the details. You can do them all in one with the export command.

First choose the calendar you want to get rid of. Select it in the calendars list, and go to the File menu and choose Export. Choose any name and location. You aren't going to need this file for very long, so save it somewhere like the desktop so you can easily get to it.

Now you are going to re-import the events into the calendar you are merging them with. Go to the File menu and choose Import. Navigate to the file you saved earlier, and click Import again. In the dialog box that appears, choose the Calendar you want to merge the events into.

If everything went OK and all the events are in one calendar, you can safely delete the other one.