The WP-Fullcalendar plugin only works on https:// pages on squat.net for some reason.

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To make this work on your squat.net website you can do the following :
First add a new page called Calendar (Or Calendrier in french, or Kalender in dutch etc.) with this shortcode in it

[fullcalendar]

Then go to -> Appearance -> Menus and add a new menu.
Fill this menu with menu entries that you want, and save it.
Make sure that your theme is going to use this new menu as menu bar.
(Usually there's at the top left of the menu section an option for that.)
Then, still in the menu section, create a custom link to your Calendar page with httpS:// in it.
After creating that custom link for the Calendar page, add that custom link menu entry to the menu as well, and save the menu.

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Some examples of the full calendar in use on squat.net websites :
https://montpellier.squat.net/?page_id=787 (french)
https://huizespoorloos.squat.net/calendar/ (dutch)
https://transfo.squat.net/calendrier (french)

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Webpage for the WP-Fullcalendar plugin :
http://wordpress.org/extend/plugins/wp-fullcalendar

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Documentation for the related "Events Manager" plugin :
http://wp-events-plugin.com/documentation
http://wordpress.org/extend/plugins/events-manager