Apticron is a debian package that emails you when there are updates that you have to install. To customize when apticron runs you can do the following:
Apticron creates two files in /var/lib/apticron and runs 24 hours after the last modification timestamp of these files. Just change the modification time of these files to customize when apticron will run everyday:
cd /var/lib/apticron sudo touch -d "-1 hour" -r cron_run *
The above command will change the modification time relative to the reference file’s modification time. The reference file is specified using the -r switch. If you omit the -r switch it will modify the time relative to the current time.