https://wiki.archlinux.org/index.php/Systemd/Timers

\cat /etc/systemd/system/certbot.service
[Unit]
Description=Renewal certificates

[Service]
Type=oneshot
ExecStart=/usr/bin/certbot renew

\cat /etc/systemd/system/certbot.unit
[Unit]
Description=Automatic renewal certificates

[Timer]
OnCalendar=daily 00:00:00
Persistent=true
 
[Install]
WantedBy=timers.target

sudo systemctl enable certbot.timer