Well, I would rather think of cron, so you don't have to type it every time, the entry in crontab would look like:
20 2 * * * /usr/bin/run-parts /etc/cron.daily 1> /dev/null
To run it daily at 2:20am
then you put your script that should run in /etc/cron.daily
The script is two liner or more, but the first line should be
which invokes commands in Bourne Shell context.
The command to edit/see scheduled jobs by cron is