What can render document Invalid?

While writing a date on any document in the upcoming year 2020, we should write it in its full format, e.g. 31/01/2020 and not as 31/01/20., because anyone can change it to 31/01/2000 or 31/01/2019 or in between any year to suit his/her convenience. That can render the document invalid.

So be cautious about this. Don't write and also don't accept it in any documents.

This problem will persist only during the year 2020.