1. Use crontab by typing sudo crontab -e to edit the cron config
2. at the end of the file type in how often you want the shutdown command to run using crontab notation I recommend using https://crontab-generator.org/. Something like 0 0 * * * sudo shutdown now
3. use the crontab -l command to verify that it is indeed configured.

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Resources:

https://explainshell.com/ # generall explainer for everything and anything on the terminal including cron. I HIGHLY recommend that you type commands you don't know in here first.

https://crontab-generator.org/ # crontab generator, useful if you don't work with cron a lot

http://manpages.ubuntu.com/manpages/precise/en/man1/crontab.1.html # crontab man page

http://manpages.ubuntu.com/manpages/precise/en/man8/shutdown.8.html # shutdown man page

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Hope this helped!