There are a lot of people who should know better who do not do that,
regardless of the benefits.
Probably the best bet would be to find how people are making the
documents and see if the tools' creators cannot be convinced to make the
tool default to add a date / time stamp.
I've written to a few authors and asked when they first published
material. Perhaps it is time for an all-out campaign to tidy up legacy
documents.
-Lars
