Looking at the Calendar contributions on the site I noticed they are out dated and do not function with the latest release, rather than rewrite a large bit of code I have made this contribution that uses the Google Calendar.
A more feature rich and better designed alternative!
Installation is easy and its a drop in contributions that requires only a limited amount of working on existing code, namely adding the link and the defines.
I have produced this is the English language but it is very easily ported to others languages.
You need to sign up with Google Calendars (free) a link is provided in the package.
Full instructions are in the ZIP file.
See it in action first here