bug#7223: DATE 8.5 and back -- Invalid date with specific dates

[Eric Blake]

On 10/15/2010 02:53 PM, Lucien Raven wrote:
> This problem was reproduced in several versions of 'date', and the oldest one I 
> could reproduce the problem was 6.10.
>
> But it doesn´t happen in older ones (tried on 'date' 5.97)

Thanks for the report.  However, this is intentional.

http://www.gnu.org/software/coreutils/faq/#The-date-command-is-not-working-right_002e

> PS: The dates correspond to the third Sunday of October.

Which is where daylight savings rules come into effect, as mentioned in 
the FAQ.  Depending on the hour of the day in which you run your command 
(since you didn't pin an exact hour in the date you were writing), you 
may have very well handed date an invalid time, in the one-hour window 
where the clocks jump around.

And reading the NEWS file:

* Major changes in release 6.0 (2006-08-15) [unstable]
...
  date: a command like date -d '2006-04-23 21 days ago' would print
  the wrong date in some time zones.  (see the test for an example)

you did indeed isolate some changes where date learned to better respect 
invalid times due to daylight savings, but where older coreutils didn't 
complain about your usage.

Meanwhile, you can resolve your issue by pinning the timezone and/or the 
hour to something other than the default of your timezone settings:

$ date +%Y --date='20101017 +Z'
2010
$ date +%Y --date='20101017 12:00'
2010

(By the way, what timezone are you in?  I could not reproduce failure in 
my timezone:
$ TZ=America/Denver date +%Y --date='20101017'
2010
)

--
Eric Blake   address@hidden    +1-801-349-2682
Libvirt virtualization library http://libvirt.org