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 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.