I remember a story a while back, before the Y2K bug fixes got going, about a chap who was booked in for some significant dental work.
The system generated a letter, based on his birth date, which only had space for the last two digits of the year, as was normal practice in the last century, until the millennium was on the horizon.
The letter instructed him that he should be accompanied by at least one parent or guardian.
He was unable to comply with this requirement, as he had no 'guardian' and he wasn't 8 years old, as the system had assumed, but 108 years old, and both his parents were unfortunately unavailable.