nginx, alias, php-fpm = File not Found

Hello everyone, I'm trying to set up nginx with DAViCal.
However, I'm getting a "File not Found" with a "FastCGI sent in stderr: "Primary script unknown" in the log.
Looks like something is wrong with my aliasing but I sure can't figure it out.

My virtual host:
server {
listen 80; ## listen for ipv4; this line is default and implied
listen [::]:80 default_server ipv6only=on; ## listen for ipv6

root /var/www-data;
index index.html index.htm index.shtml index.php;

server_name that.random.server;

location / {
ssi on;
}

location ~ \.php$ {
#try_files $uri =404;
include /etc/nginx/fastcgi_params;
fastcgi_split_path_info ^(.+\.php)(/.+)$;
fastcgi_pass unix:/var/run/php5-fpm.sock;
fastcgi_index index.php;
}

location /calender {
alias /usr/share/davical/htdocs;
}
}

#############################################################

My FastCGI-params:
fastcgi_param QUERY_STRING $query_string;
fastcgi_param REQUEST_METHOD $request_method;
fastcgi_param CONTENT_TYPE $content_type;
fastcgi_param CONTENT_LENGTH $content_length;

fastcgi_param SCRIPT_FILENAME $request_filename;
fastcgi_param SCRIPT_NAME $fastcgi_script_name;
fastcgi_param REQUEST_URI $request_uri;
fastcgi_param DOCUMENT_URI $document_uri;
fastcgi_param DOCUMENT_ROOT $document_root;
fastcgi_param SERVER_PROTOCOL $server_protocol;

fastcgi_param GATEWAY_INTERFACE CGI/1.1;
fastcgi_param SERVER_SOFTWARE nginx/$nginx_version;

fastcgi_param REMOTE_ADDR $remote_addr;
fastcgi_param REMOTE_PORT $remote_port;
fastcgi_param SERVER_ADDR $server_addr;
fastcgi_param SERVER_PORT $server_port;
fastcgi_param SERVER_NAME $server_name;

fastcgi_param HTTPS $https;

# PHP only, required if PHP was built with --enable-force-cgi-redirect
fastcgi_param REDIRECT_STATUS 200;

###############################################################

I'd be really glad if someone would help me sort that out.

So long,
deux