Re: dates before 1970

[Eric S Fraga <e.fraga@ucl.ac.uk>]

Nick Dokos <nicholas.dokos@hp.com> writes:

> Eric S Fraga <e.fraga@ucl.ac.uk> wrote:
>
>> This is a sort of bug report but possibly more a curiosity...
>> 
>> I imagine this has something to do with time 0 in Unix but I cannot seem
>> to be able to enter any date earlier than 1 Jan 1970 using C-c! (say).
>> However, once I have entered a date (later than that), I can use
>> S-<down> on the year to get to the date I want.  This seems rather
>> inconsistent?
>> 
>> To be precise, I get the wrong date recorded if I try:
>> 
>>   C-c ! 1968-12-10 RET
>> 
>> (where C-c ! is =org-time-stamp-inactive=).
>> The result is =[2011-12-10 Sat]=
>> 
>> The bug is not so much that I cannot input dates I want but that the
>> inactive timestamp generated is *incorrect* and yet there is no error
>> message.
>> 
>
> Good one! The culprit is org-read-date-analyze which near the end contains
> this snippet of code:
>
> ,----
> |     ...
> |     (if (< year 100) (setq year (+ 2000 year)))
> |     (if (< year 1970) (setq year (nth 5 defdecode))) ; not representable
> |     (setq org-read-date-analyze-futurep futurep)
> |     (list second minute hour day month year)))
> `----
>
> The trouble is that the caller (org-read-date) takes the result and
> does a round-trip through the emacs time encode/decode functions to make
> sure the result is sane. Dates before 1970 would break that (I get (0 9
> 10 26 11 2033 6 nil -18000)) so it seems it wraps around to 2033 or
> so).

Yes, that makes sense.

> In addition, most callers of org-read-date call it with a non-nil
> to-time argument: that makes it return an emacs-encoded time (which is
> then manipulated as such and which I believe has to satisfy the >=1970
> requirement).
>
> So I'd guess raising an exception might be the simplest way to deal with
> this. Here's a patch to try out:

This seems to work fine.  Thanks.

I am glad, however, that I can enter any date and then use the S-<down>
etc. keys to get the date I want.  Of course, I am not sure if anything
else in org breaks as a result...  org-sparse-tree with very old
scheduled dates seems to work.  Haven't tried much else and I would
guess few would notice?

Thanks again,
eric

-- 
: Eric S Fraga (GnuPG: 0xC89193D8FFFCF67D) in Emacs 24.0.50.1
: using Org-mode version 7.5 (release_7.5.27.gefa56.dirty)