Nginx auto access log rotate

server {
if ($time_iso8601 ~ "^(\d{4})-(\d{2})-(\d{2})") {
        set $year $1;
        set $month $2;
        set $day $3;
    }
access_log  logs/access_log_$year$month$day  main if=$loggable;
...
...
}

There is a bug somewhere ,but it work