Calendar Firefox OS app, see https://schnark.github.io/install.html?id=calender for more information.

Note that this repository is managed as described in https://xkcd.com/1597/.

And, yes, the name is misspelled, and, no, I wo'n't change it (and, no, "wo'n't" is spelled correctly, see the preface to Sylvie and Bruno Concluded).