As you may know, we are in the process of rewriting the server part of Cozy, to migrate it from Node.js to Go. This will require to adapt every application. We plan to work on Calendar during the third quarter of 2017.
The come back of the week view is one of the most requested features of Cozy, so I hope we will add it to our roadmap when we'll migrate the application.
The demo site runs a pretty old version of Cozy, that's why the week view is still available. We disabled it a few months ago because it was quite buggy and we wanted to focus on some tasks with higher priorities.