Linux users: Setting up read access for your Google Calendar from the integrated Gnome calendar (included with Evolution) can be achieved with one terminal command. In fact, it is surprisingly simple to set up a self-updating subscription to your Google Calendar. You only need to enter the following command once and your calendar will automatically update.
Go to your Google Calendar and find out your private ICAL URL (This can be found after clicking Manage Calendars > Your Calendar Name) Now, open a terminal and type :
That's all there is to it. The dialog shown in the screenshot will appear and you'll be able to customise how frequently you want the Gnome calendar to update. When you click the calendar in the Gnome menubar, your events will be displayed.