Seems to me your new HTTP protocol would support this, maybe? Date
could just be one of the return values. However, it would be nice to
be able to determine the last-modified date for a document remotely
without actually having to fetch the whole document (pardon me if I'm
missing something since I haven't read your new HTTP stuff yet).
Timestamps would be a great enabling mechanism for computer-assisted
browsing of the Web.
Marc