Quote:If you run Debian testing/unstable and ever installed anacron 2.3-33 on
a systemd based system, then anacron will no longer be enabled and the
daily/weekly/monthly cron jobs will not be run until it is.

Since not all cron jobs have migrated to systemd timers, Debian
testing/unstable systems with systemd and anacron may be missing
some essential cron jobs, such as making backups of aptitude state.

To see if a system is affected you can use these commands:

zgrep -i anacron.*2.3-33 /var/log/apt/history.log*
systemctl status anacron.service anacron.timer

To re-enable anacron you can use these commands:

sudo systemctl enable anacron.service anacron.timer
sudo systemctl start anacron.service anacron.timer

More details of this problem are available in these bugs:

https://bugs.debian.org/1019554
https://bugs.debian.org/1020966
https://bugs.debian.org/1021496