This is a virus detection. Viruses are programs that self-replicate recursively, meaning that infected systems spread the virus to other systems, which then propagate the virus further. While many viruses contain a destructive payload, it's quite common for viruses to do nothing more than spread from one system to another.
Indication of Infection
The above message displayed on 23rd day of any month.
Methods of Infection
Overwrites up to four documents on the recent files list and all *.doc files on drive C: with a copy of the active infected document.