Subject: bug#17161: closed (Re: bug#17161: Bug in date arithmetic of date)

From: [email-masked] (GNU bug Tracking System)
Date: Tue, 01 Apr 2014 16:06:04 +0000

Your bug report

#17161: Bug in date arithmetic of date

which was filed against the coreutils package, has been closed.

The explanation is attached below, along with your original report.
If you require more details, please reply to [email-masked].

-- 
17161: http://debbugs.gnu.org/cgi/bugreport.cgi?bug=17161
GNU Bug Tracking System
Contact [email-masked] with problems

Subject: Re: bug#17161: Bug in date arithmetic of date
From: Eric Blake <[email-masked]>
To: "Marc R.J. Brevoort" <[email-masked]>, [email-masked]
Date: Tue, 01 Apr 2014 10:05:27 -0600
List-Id: <debbugs-submit.debbugs.gnu.org>

tag 17161 notabug
thanks

On 04/01/2014 05:30 AM, Marc R.J. Brevoort wrote:
> Hi,
> 
> There seems to be some weirdness in date arithmetic when dates
> include a time stamp (and all provided in ISO formatting):

The weirdness is caused by your choice of locale, coupled with your
government's use of daylight savings, and not a bug in 'date'.

See also the FAQ:
https://www.gnu.org/software/coreutils/faq/coreutils-faq.html#The-date-command-is-not-working-right_002e

> mrjb@THE-D-MRJB:~$ date -d "2014-03-11 12:34 -2 hours" +"%Y-%m-%d %H:%M:%S"
> 2014-03-11 15:34:00
> mrjb@THE-D-MRJB:~$ date -d "2014-03-11 12:34 +2 hours" +"%Y-%m-%d %H:%M:%S"
> 2014-03-11 11:34:00
> mrjb@THE-D-MRJB:~$ date -d "2014-03-11 12:34 -1 day" +"%Y-%m-%d %H:%M:%S"
> 2014-03-12 13:34:00
> mrjb@THE-D-MRJB:~$ date -d "2014-03-11 12:34 +1 day" +"%Y-%m-%d %H:%M:%S"
> 2014-03-12 11:34:00

These examples happen to cross a daylight savings boundary in your
current locale.  If you would amend your example to include time zone
names, you would see the name change, as evidence that the dates listed
are really 2 (or 24) hours apart, even though the wall clock time
appears to be 1 hour off.

You can also force date to operate on --utc, which does not observe
daylight savings, and therefore is immune to these oddities.

As such, I'm closing this as not a bug.

-- 
Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org

Subject: Bug in date arithmetic of date
From: "Marc R.J. Brevoort" <[email-masked]>
To: [email-masked]
Date: Tue, 1 Apr 2014 13:30:16 +0200 (CEST)
List-Id: <debbugs-submit.debbugs.gnu.org>

Hi,

There seems to be some weirdness in date arithmetic when dates
include a time stamp (and all provided in ISO formatting):

Correct:

mrjb@THE-D-MRJB:~$ date -d "2014-03-11" +"%Y-%m-%d %H:%M:%S"
2014-03-11 00:00:00

mrjb@THE-D-MRJB:~$ date -d "2014-03-11 -1 day" +"%Y-%m-%d %H:%M:%S"
2014-03-10 00:00:00

Incorrect:

mrjb@THE-D-MRJB:~$ date -d "2014-03-11 12:34 -2 hours" +"%Y-%m-%d 
%H:%M:%S"
2014-03-11 15:34:00
mrjb@THE-D-MRJB:~$ date -d "2014-03-11 12:34 +2 hours" +"%Y-%m-%d 
%H:%M:%S"
2014-03-11 11:34:00
mrjb@THE-D-MRJB:~$ date -d "2014-03-11 12:34 -1 day" +"%Y-%m-%d %H:%M:%S"
2014-03-12 13:34:00
mrjb@THE-D-MRJB:~$ date -d "2014-03-11 12:34 +1 day" +"%Y-%m-%d %H:%M:%S"
2014-03-12 11:34:00