/lib/systemd/system/certbot.timer

/lib/systemd/system/certbot.timer

Description=Run certbot twice daily

[Timer]
OnCalendar=*-*-* 00,12:00:00
RandomizedDelaySec=43200
Persistent=true

[Install]
WantedBy=timers.target

See also

• Systemd: systemctl, systemd-journald, journalctl systemd-cat, systemd-logind, systemd-networkd:networkctl, systemd-timesyncd, systemd-resolved, systemd-udevd , Systemd-logind: loginctl, hostnamectl, udevadm, systemd-run, portablectl, systemd-nspawn, systemd resource management, Timer (systemd), systemd logs, /etc/systemd/, systemd services, systemd-mount, /run/systemd/, .service, /usr/lib/systemd/, /usr/lib/systemd/system/, /usr/lib/systemd/system/systemd-resolved.service, /lib/systemd/, machinectl, systemd-oomd, systemd-analyze
• Certbot, Let's Encrypt: certbot (command), plugins, OCSP, certbot certificates, certbot renew (examples), /var/log/letsencrypt/letsencrypt.log, Certificate Checker, Certbot changelog, certbot --help, /etc/letsencrypt/

https://wiki.ubuntu.com/DebuggingSystemd