Fancy receiving congratulations on the anniversary of when you installed your system?
Installing the installation-birthday package on your Debian machines will celebrate each birthday of your system by automatically sending a message to the local system administrator.
The installation date is based on the system installation time, not the package itself.
installation-birthday is available in Debian 9 ("stretch") via the stretch-backports repository, as well as in the testing and unstable distributions:
$ apt install installation-birthday
Enjoy, and patches welcome. :)