From: Lars Ingebrigtsen <larsi@gnus.org>
   Date: Sun, 26 Dec 2021 12:31:07 +0100

   Better errors messages are possible without making many specific error
   symbols, though.

OK, I think I have a good solution that uses a single error symbol; let
me know what you think.  (Having never done much with Elisp conditions,
I was still thinking in terms of Common Lisp, so I had to go scratch my
head for a while.)

   I am currently working on broadening what the parser will accept,
though I think it is close to a usable state.  I am using the
documentation for the Perl Date::Parse module to see what it accepts,
and will then look at the corresponding Python and Ruby modules for
further ideas.  I am not planning to adopt everything I see, though; in
particular, I think it's a good idea for new code to stick to insisting
on four-digit years except when the caller has specified a format that
determines the month/day order.

					-- Bob