If you are looking for syncing your Mozilla Thunderbird with Google Calendar, then here it is:

Google Calendar Thunderbird

To sync your Thunderbird with Google Calendar, you must first install Thunderbird Calendar.
After installing Thunderbird Calendar, you have to install an add-on Provider for Google Calendar, which allows you to view, add, edit and delete your Google Calendar Events etc. within Thunderbird Calendar. Soon you made any changes, it will get synced with the Google Calendar, which you can confirm by viewing your Calendar on the Google Calendar website.

Provider for Google Calendar

To install Provider for Google Calendar, goto the direct url of the add-on below:
https://addons.mozilla.org/en-US/thunderbird/addon/4631/

Or goto the Thunderbird Addons website, and search for Provider for Google Calendar through the following link:
https://addons.mozilla.org/en-US/thunderbird/addon/4631/

Hopefully this will help you sync your Thunderbird with Google Calendar.