When the year 2020 is abbreviated on official forms and documents, those looking to exploit unsuspecting people can easily manipulate those numbers and leave people potentially vulnerable to fraud.
For example, a document dated 1/4/20 can easily be changed to 1/4/2021 by adding two numbers at the end.
There are several ways that could pose a problem. Rheingold cited the example of a stale check, or one that was written more than six months or so ago. If you have an old check lying around that’s dated 1/4/20 and someone finds it, they could add “21” to the end of that date, and voila, the check is no longer stale.