A visitor book is a list of people who came to your building — exactly the kind of record a data-protection regulator asks about. The honest answer is a window that actually deletes, so this page does.
After the window below, a finished visit is deleted along with its badge record and the site rules it accepted, and any visitor left with no visits at all goes with it. Anyone still on site is never in scope, whatever the calendar says: somebody inside the building cannot be forgotten.
Run it on a schedule
The button above is the same code the cron runs. Add one line to your crontab and the window enforces itself:
17 3 * * * /usr/bin/php /var/www/html/cron/purge.php >> /var/log/visitora-purge.log 2>&1
The scheduled purge has never run on this install. Until you add that line, deleting is something you do by pressing the button.
Visitora records arrivals and departures. It is not a legal-advice tool: the right retention period for your building is a decision you or your data-protection adviser make, and this page only enforces the number you set.