[Unit]
Description=Dynamic DNS record update, every other day
ConditionHost=mainframe

[Timer]
# Matches the retired cron line: 0 2 */2 * *. systemd needs an explicit
# start value for the day-of-month step; a bare */2 fails to parse.
OnCalendar=*-*-1/2 02:00:00
Persistent=true

[Install]
WantedBy=timers.target