Forgive me, as my comment is uninformed. But, a time/date stamp implies that there is a program that is able to determine the correct date. How can a battery vehicle be accurate, where does it get a current date??
Another question, I understand that a backup process is just that; A backup. If a time/date stamp were an issue, there must be a program that can determine if it changed. Input --> Process --> Output. I am not familiar of a backup procedure that is procedural. Educate me please, cause I don't know about flash stuff.