Pressing the "Calendar" button on the main nav bar (just below the logo) causes a page - http://forums.scribus.net/index.php?action=calendar - to be served which says:
An Error Has Occurred!
Invalid year value.
This happens when either logged in or not.
(I only found this out by accident, I don't know if this calendar has ever worked before.)
i could not find where the calendar can be deactivated...
but i've now made it visible to no groups... so it's a bit of the same.
if somebody wants to use the calendar i can re-enable it and check what the error is.