First disable the existing /etc/cron.daily/logrotate. A nice way to do so is to rename it as /etc/cron.daily/logrotate.disabled. That way it is easy to restore it if and when you want and clear that it has been disabled.
Then set up a scheduled job to replace it. Three options:
- root's crontab
- An /etc/cron.d file
AFAIK "the Debian way" is to use root's crontab (/etc/crontab is installed by package so best not changed and IIRC /etc/cron.d is intended for packages, not sysadmins to create files in).
As root, use the crontab -e command (taking care not to key r instead of e!) and create a line:
30 20 * * * /usr/sbin/logrotate /etc/logrotate.conf
EDIT: that's not really your /etc/cron.daily/logrotate file is it?!