Re: don't-know values for file-attributes?

[Richard Stallman]

    When a filename handler doesn't know the ctime, mtime, or atime of a
    file, what should file-attributes return?  Ange-FTP seems to say that
    (0 0) is the way to express this.

The clean thing to do would be to use nil for that case.  That may be
an incompatible change that would require checking the callers and
changing them, but I think the number of programs that would break is
fairly small, so the change would be worth making if someone wants to
do the work.