Calender link only works when logged in as admin

When I click on the link when I'm logged in as an admin, I see the calendar.
However, when I login as a normal user or when I'm not logged in, I get redirected to http://www.domain.com/user?destination=month.php and I get an error that the webpage cannot be found.

I have "access webcal" enabled for both anonymous and authenticated user. I also tried enabling all the webcal permissions, this doesn't make any difference.