[ubuntu-za] Calendar for Thunderbird

[Wikus]

Afternoon all ,

I want to add a calendar to Thunderbird. I did searching and it seems 
the add-on lightning is good.
BUT , on their site it shows lightning is not available for Thunderbird 
11.0.1 (which is the version I am using)
I am aware of the google calender add-on , but I want a calendar that 
will work when I am offline also.

Any other good Thunderbird calendar add-ons ?

Thank you

- Wikus