Just fixed my problem completely now :)

For anyone who also uses Lua and wants to overcome this cross browser compatibility issue with expires and max-age cookie vars.

if ($host ~* www(.*)) {
set $host_without_www $1;
}
set_by_lua $expires_time 'return ngx.cookie_time(ngx.time()+2592000)';
add_header Set-Cookie "value=1;domain=$host_without_www;path=/;expires=$expires_time;Max-Age=2592000";

http://www.networkflare.com/