I updated the Wikipedia article to reflect this coming problem. It won't be just ISO 9660. There are tons of software out there that measures their date since 1900 - the question is how much of it uses a single signed byte?

https://en.wikipedia.org/wiki/Time_formatting_and_storage_bu...

About storing years as 11 bit. That piece is what we used to call FUD. There is no mention of any such implementation.