Update 10/17/2011: I have updated the links for both Lightning and Provider for Google Calendar add-ons. Also added the note about needing to know the version of Thunderbird in order to choose the correct version of Lightning.

I started using Gmail (words I never thought I’d say) earlier this year because I needed a Gmail account to use with the Android Marketplace. Plus my college uses the Gmail system for their email and calendar. In the past couple months I started using the Google Calendar as well. In the past I have looked at and even tried using Mozilla Lightning add-on for Thunderbird as well as the standalone Sunbird application, but had run into issues. There has been a lot of discussion in the Thunderbird Builds about Lightning lately, especially with the release of Thunderbird 5.0 on June 28th.

I had read prior about integrating your Google Calendar into Lightning. Since I already had Lightning working in Thunderbird 5.0, I decided to give it a go. There are two parts to this, you will need to have installed the newest version of both Lightning and the Provider for Google Calendar (allows you to sync your calendar between the web based Google Calendar and Lightning) add-ons.

IMPORTANT: You will need to know what version of Thunderbird you are using in order to choose the correct version of Lightning. From Thunderbird go to Help > About Thunderbird and make note of what version you are running. Installing the incorrect version of Lightning will result in a blank calendar. If this happens, go back and install the correct version.

Install the add-ons

1. Download Lighting (be sure you know which version of Thunderbird you are running).
2. Download Provider for Google Calendar
3. Install the add-ons by dragging the downloaded files into Thunderbird’s Add-ons manager
4. Restart Thunderbird to complete the installs.

Integrating Google Calendar into Lightning

1. In Thunderbird click on the Calendar Tab
2. In the left column in the Calendar section, right-click and select New Calendar…
   
3. The Create New Calendar window will open. Select On the Network and click Next >
   
4. Select Google Calendar
   
5. In your browser go to your Google Calendar. Click the arrow next to the calendar you want to use. Click Calendar setting
6. Your calendar details window will open. If needed, click on the Calendar Details tab. At the very bottom in the Private Address section click the XML button.
   
7. Your calendar’s Private Address will popup in a new window. Copy this address.
   
8. Go back into Thunderbird and Lightning. Paste the address from step #7 into Location field from step #4. Click Next >
9. You should have an authentication window popup, prompting you to sign into your GMail account. Also another Create New Calendar window will open asking you to choose a name and color for your calendar. Enter this information and click Next >
   
10. You are done! Your Google Calendar is now in Lightning.
    
11. Repeat this process if you have more calendars you need to add. In my case I added my school calendar and the US Holidays calendar (same process except step #6 select XML for calendar address and you need to authenticate on step #9 with your gmail account info).
12. If your Google Calendar(s) is/are going to be the only calendar(s) you will be using in Lightning, you can remove the default ‘Home’ calendar by right-clicking and select Delete Calendar (this can only be done if there is more than one calendar setup).