BusyCal

To use the Google Calender on Mac you have to install BusyCal.

Installation

To install BusyCal you have to buy a license from the Website: http://www.busycal.com/. When you have received the serial key, you can download the application from the same page where you bought it.

Connect to Google Calendar

To connect to a Google Calendar, you have to go into settings and then you have to choose "Connect to Google Calendar" as shown in the picture

Now you have to insert the data of your Google account into the popup that appears.

Activate the calendars

Now you can activate the calendars you want. They will appear after a few seconds. Finally the programm is activated and it will sync your Google Calendar automaticly with your BusyCal.