I will always put a date on every report or document I produce, that is not going to get one added automatically. (E.g., blog entries and emails get a time stamp added; I don't have to.)
I bet that literally half of the papers—white papers and other reports—I find on the Internet have no indication of when they were written. If I am looking for something on, let's say, "Traffic Generation Systems," (network test devices), and I find a paper "LARIAT: Lincoln Adaptable Real-time Information Assurance Testbed, I believe it would be nice to have, somewhere clearly visible, an indication of when it was written. I am not picking on the writers of this paper. As I said, probably half of the academic reports on the Internet suffer from a lack of a time stamp indicating when it was written.