Time to add your scripts into crontab schedule: To set crontab, a built-in scheduler:
[pi@raspberrypi ~]# crontab -e
And copy and paste this into a newline in the file that opens: 00 20 * * /bin/startmotion.sh 00 08 * * /bin/stopmotion.sh
Save the file as usual. And you're done!
To list your scheduled task(s) in crontab: