GNU bug report logs - #14146
[date command] Possible bug

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Message #5 received at submit <at> debbugs.gnu.org (full text, mbox):

From: Ivan Lombardi Borgia <ivan.lombardiborgia <at> gmail.com>
To: bug-coreutils <at> gnu.org
Subject: [date command] Possible bug
Date: Fri, 5 Apr 2013 11:13:04 +0200

[Message part 1 (text/plain, inline)]

Good morning,

for the 1th of April 2013 the command *date *has this interesting behaviour:
*
*
*$ date*
*Mon Apr  1 00:22:31 CEST 2013*
*$ date -d 'yesterday'*
*Sat Mar 30 23:22:38 CET 2013*
*
*
As you can read the date is 30 March instead of 31 the time 23:22 instead
of 00:22

I could verify that on:

   - my personal machine running:
   Linux dip03-ubu 3.2.0-40-generic-pae #64-Ubuntu
   date --version: date (GNU coreutils) 8.13
   - production servers running:
   Linux ecomappsrv01 2.6.38-8-generic-pae #42-Ubuntu
   date --version: date (GNU coreutils) 8.5

That doesn't happen for year 2012 and 2014.
It happens even using -u option.
It does not happen forcing date:
*date -d '2013-04-01 00:22:00 1 day ago' *
*Sun Mar 31 00:22:00 CET 2013*
*
*
If you need more information just ask and I will try to respond as soon as
possible.

Thank you, best regards.


Ivan Lombardi Borgia

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Message #12 received at 14146-done <at> debbugs.gnu.org (full text, mbox):

From: Eric Blake <eblake <at> redhat.com>
To: Ivan Lombardi Borgia <ivan.lombardiborgia <at> gmail.com>
Cc: 14146-done <at> debbugs.gnu.org
Subject: Re: bug#14146: [date command] Possible bug
Date: Fri, 05 Apr 2013 09:24:27 -0600

[Message part 1 (text/plain, inline)]

tag 14146 notabug
thanks

On 04/05/2013 03:13 AM, Ivan Lombardi Borgia wrote:
> Good morning,
> 
> for the 1th of April 2013 the command *date *has this interesting behaviour:
> *
> *
> *$ date*
> *Mon Apr  1 00:22:31 CEST 2013*
> *$ date -d 'yesterday'*
> *Sat Mar 30 23:22:38 CET 2013*

Did you notice the change in the time zone name from CEST to CET, based
on daylight savings?

> That doesn't happen for year 2012 and 2014.

Yeah, because daylight savings in your timezone falls on a different
date in those years.

> If you need more information just ask and I will try to respond as soon as
> possible.

You are hitting a typical usage problem.  This is not a bug in date, but
in your usage of it; you are failing to account that "yesterday"
translates to "24 hours ago", but that 24 hours ago close to midnight
when crossing over a 23-hour day (thanks to daylight savings) can cross
2 calendar days.

For more information, including the tip to base relative date
computation on noon instead of close to midnight, see the FAQ:

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

As such, I'm closing this as not a bug, although you may feel free to
continue replying if you have further questions.

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

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