Comment 14 for bug 174672

I'm not totally sold that just automatically adding the locale calendar is the right thing to do. It seems to me that there are so many cases when this is going to be not something the user wants that it makes sense to be a bit more conservative here. Cases include users who live in places which are not likely to see a lot of localizations (eg en-CA, de-AT) since existing ones (eg en-US, de-DE) tend to be good enough, or places that have few enough people that they don't see localizations until much later in the cycle.

A couple of possible strategies I can think of include:

a) have a menu item that simply brings up <http://www.mozilla.org/projects/calendar/holidays.html>. This could either be in a <browser> element in Sunbird/Lightning or the OS-default web-browser. The latter presumes that we automatically register ourselves as the OS-default ICS calendar and automatically subscribe to any calendars when handling such a file.

b) have some sort of slightly more sophisticated interface, perhaps triggered from a menu item, that knows about the set of available holiday calendars and uses the locale-calendar as the default choice there