borg-backup-daily.timer

[Unit]
Description=Run Borg backup daily.

[Timer]
# Format: [weekday] year-month-day hour:minute:second [timezone]
# The storage server is restarted daily at 00:00:00. Run shortly after reboot.
OnCalendar=*-*-* 00:15:00

# Store last run time. Run unit immediately after boot, when runs were skipped.
# For example because the computer was switched off.
Persistent=true

[Install]
WantedBy=timers.target