Re: Timestamps for a whole year, or a year and month

[Erik Hetzner <egh@e6h.org>]

At Mon, 30 Dec 2013 20:11:17 +0000,
Eric S Fraga wrote:
> 
> Erik,
> 
> I am not sure but I remember having a discussion about the problems with
> dates that precede time 0 in Unix which corresponds to 1 January
> 1970.  See man page for ctime(3) for instance.
> 
> I am currently offline (in the tunnel under the North Sea :-) so cannot
> find out what the conclusions of our discussion may have been.  Please
> search the mailing list on Worg.

Hi Eric,

This looks to be the main thread on the issue:

http://thread.gmane.org/gmane.emacs.orgmode/39206

I have set org-read-date-force-compatible-dates to nil and tested on
two different emacs, one 32 bit and one 64 bit:

  GNU Emacs 24.3.1 (x86_64-pc-linux-gnu, GTK+ Version 3.8.4) of 2013-10-03 on menkib, modified by Debian
  GNU Emacs 24.3.1 (i686-pc-linux-gnu, GTK+ Version 3.6.4) of 2013-10-03 on elnath, modified by Debian

For the 64 bit system, I can get accurate dates back until 1583
(comparing with the calendar here:
http://www.arc.id.au/Calendar.html). This is just before the Gregorian
calendar was introduced. (Of course this depends on your locale :)
since some countries were a little slower introducing it.)

Using dates before that generates the wrong day of the week, but
doesn’t seem to cause an error. It seems that I am also able to enter
dates up until year 9999 and get the correct day of the week (as
compared with the output of the cal command).

On the 32 bit machine using dates before 14 Dec 1901 or after 18 Jan
2038 throws an error:

  Debugger entered--Lisp error: (error "Specified time is not representable")
    encode-time(0 0 0 13 12 1901 (nil nil nil))

So using 32 bit emacs does seem to be a problem.

It is strange to me that dates before 1970 seem to work fine on both
machines.

best, Erik

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