This feature is available with artica version 1.4.021711
If you are under this release you need to upgrade your Artica version.
If this version is not released use the How to upgrade Artica to a nightly build ?
This Filter allow you to add a "Calendar" trough RoundCube interface.

RoundCube Calendar is a calendar plugin for RoundCube Webmail written by Lazlo Westerhof. The calendar is based on jQuery fullcalendar
Features
- full calendar
- add/edit/remove events
- custom backend support
- basic event categories
- export events to ICS

To install it you need to install RoundCube 3.x version.
If RoundCube 3.x version is installed you will be able to access to the feature:
- On the left menu, click on "Messaging"
- Select "Mailboxes" tab.
- Select RoundCube WebMail System icon
- Click on "settings" tab under the RoundCube area.
- Click on "Mailbox Filters Plugin" Icon
- Select "RoundCube Calendar"
- Turn to green in order to activate the plugin





