Debian :: Apt-mirror Not Running At Regular Interval

I use apt-mirror to sync a local copy of Debian repo on my HDD. I recently reinstalled my Debian setup, and now I can't seem to make apt-mirror run at regular intervals!? As far as I can recall (and as mentioned on different sites) all I have to do is edit /etc/cron.d/apt-mirror

I tried adding the following lines, but nothing works

Code: Select all0 0,6,12,18 * * * apt-mirror    /usr/bin/apt-mirror > /var/spool/apt-mirror/var/cron.log
Code: Select all0 0-23/6 * * * apt-mirror    /usr/bin/apt-mirror > /var/spool/apt-mirror/var/cron.log

Also, the log file is empty!!