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bug#11098: date --yesterday wrong result
From: |
Eric Blake |
Subject: |
bug#11098: date --yesterday wrong result |
Date: |
Mon, 26 Mar 2012 11:31:57 -0600 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:11.0) Gecko/20120316 Thunderbird/11.0 |
tag 11098 notabug
thanks
On 03/26/2012 05:31 AM, Hugo Guérineau wrote:
> Dear Mister, Madam,
>
> I'm writing to report a date computation problem.
>
> The command "date --date='yesterday' +%Y-%m-%d" launched this morning
> between 0:00 am and 0:59 am gives the wrong result:
>
> address@hidden:> date --date='today' +%Y-%m-%d; date --date='yesterday'
> +%Y-%m-%d
> 2012-03-26
> 2012-03-24
>
> This is caused by the system clock changes which happened last night.
Thanks for the report. However, this is not a bug in date, but in your
expectations. 'yesterday' translates to '24 hours ago', and due to your
daylight savings swap, 24 hours ago really does put you into a different
date. As recommended in our FAQ,
https://www.gnu.org/software/coreutils/faq/#The-date-command-is-not-working-right_002e
it's almost always better to base relative time computations off of noon
rather than midnight (as both 11 am and 1 pm fall in the same day, even
when your multiple-of-24-hours crosses a 23-hour or 25-hour day).
--
Eric Blake address@hidden +1-919-301-3266
Libvirt virtualization library http://libvirt.org
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