Document date and last updated date

["Sebastien Vauban" <wxhgmqzgwmuf-geNee64TY+gS+FvcfC7Uqw@public.gmane.org>]

Hi,

Following this discussion, I think that we could discuss some related
features, as exporters are currently evolving and certainly will support new
stuff.

Nicolas Goaziou wrote:
> tsd-P0awH739Ni4AvxtiuMwx3w@public.gmane.org (Thomas S. Dye) writes:
>> Nicolas Goaziou <n.goaziou-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> writes:
>
>>> There are three states for creator, on, off and comment, and two places to
>>> insert the information (in hypersetup and at the end of the exported
>>> data).
>>>
>>> What would be a correct way to handle the different configurations here?
>>
>> Perhaps:
>>
>>   - off, no information is inserted
>>   - on, information is inserted in \hypersetup{} and as text at the end of
>>     the file
>>   - comment, information is inserted in \hypersetup and as a comment at the
>>     end of the file.
>
> This is now the case. Thanks.

Speaking of hyperref and its _document properties_, it makes me think of a
generic point for which I don't have yet a really satisfactory solution, that
is about handling dates.

In a PDF document, regarding dates, we have (see output of `pdfinfo'):

- creation date
- modification date

In Org, we have the `#+DATE:' info keyword, with the date that's supposed to
be exported onto the final document format (HTML, PDF, OOo, etc.).

But we don't see when the document has been updated for the last time --
neither when it has been created.

For the former point (date of last update), I've customized Org so that the
`time-stamp' package updates time stamps every time you save the Org buffer:

#+begin_src emacs-lisp
  (add-hook 'before-save-hook 'time-stamp)

  (add-hook 'org-mode-hook
            (lambda ()
              ;; file modification date
              (set (make-local-variable 'time-stamp-format) "%:y-%02m-%02d")
              (set (make-local-variable 'time-stamp-start) "^#\\+DATE: +")
              (set (make-local-variable 'time-stamp-end) "$")))
#+end_src

That makes my `#+DATE:' info keyword always *up-to-date*.

Though, in some cases:

- I must print a document with a future date (for example, I'm preparing
  slides which I will present on next Monday) -- hence, the above breaks this,
  because I'd like to have next Monday's date already printed on my slides (at
  least on the title page).

- it would be nice to get keep track of the creation date of the Org document,
  though this is not really necessary.

Clearly, I should not make the `#+DATE:' info keyword updated, to keep it for
its export function (as the official date to be printed on the title page),
but then it'd be good to have at least a last modification date somewhere.

What do you think of all this?  How do you do to keep more info on dates?

Best regards,
  Seb

PS- Some global `draft' or `final' info could make some sense too.

-- 
Sebastien Vauban