Hi wmichaelb, Please as the add on developer this question. If you would like to change the calendar name, please click on the button on the top right of the thunderbird screen, double click on the calendar name and edit the name in the window that pops up.

Hope this helps!

guigs2: I appreciate your kind response. But please let me clarify: it's not the calendar's title that I'm trying to change, but the notation of which week of the year the calendar has noted. When printing the weekly task view, the calendar's title is at the top. A subheading is then available to edit as well. But what I'd like to edit is the third heading, which this week reads "Week 10". It's the "Week 10" that I'd like to edit. Is there an entry in a configuration file that I could edit, or ???

Thank you for your time and interest!

I think the answer to this is you can't. I did spend some time looking trough the source code back when you first posted and I see nothing that looks like an option even at the source level. I have filed a bug seeking to rename it to the calendar title, https://bugzilla.mozilla.org/show_bug.cgi?id=982473 so we will just have to see how it goes. You might vote for the bug, as more votes usually raises a bug out of the masses.