[debbugs-tracker] bug#23008: closed (Daylight Savings Time Bug in Date)

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Your message dated Mon, 14 Mar 2016 09:04:16 -0600
with message-id <address@hidden>
and subject line Re: bug#23008: Daylight Savings Time Bug in Date
has caused the debbugs.gnu.org bug report #23008,
regarding Daylight Savings Time Bug in Date
to be marked as done.

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23008: http://debbugs.gnu.org/cgi/bugreport.cgi?bug=23008
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--- Begin Message --- Subject: Daylight Savings Time Bug in Date Date: Mon, 14 Mar 2016 01:24:40 -0400 User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.5.1

We detected a bug in the date program, which correlates to the daylight savings time change. A day disappeared from the date program between 12:00 AM and 1:00 AM on 3/14/16. The date program began working as expected immediately after 1:00 AM. Here is the bizarre output that I got for basic commands on 3/14/16:

$ date -d -0days +%Y-%m-%d
2016-03-14

$ date -d -1days +%Y-%m-%d
2016-03-12

Notice that I was unable to obtain the expected output of 2016-03-13 for the day prior. I was able to reproduce this using version 8.13 on Debian, and 8.21 on Mint.

--
Sarah C. Corriher
Co-author of "Defy Your Doctor and Be Healed"
336-528-4120
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--- End Message ---

--- Begin Message --- Subject: Re: bug#23008: Daylight Savings Time Bug in Date Date: Mon, 14 Mar 2016 09:04:16 -0600 User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.6.0

tag 23008 notabug
thanks

On 03/13/2016 11:24 PM, Sarah Corriher wrote:
> We detected a bug in the date program, which correlates to the daylight
> savings time change.

Thanks for the report.  However, this is not a bug, but a FAQ that gets
asked twice a year.  See:

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

> 
>    $ date -d -0days +%Y-%m-%d
>    2016-03-14
> 
>    $ date -d -1days +%Y-%m-%d
>    2016-03-12

When trying to add units of 24 hours (the -1days), only to then display
just a day and not an hour, it's best to start from noon rather than
from a time that might be impacted by daylight savings:

# date -d '12:00pm 2014-03-14 -1day' +%Y-%m-%d
2016-03-13

Otherwise, as you discovered, starting at midnight and going 24 hours
across a day with only 23 hours is likely to skip that day.

I'm closing this as not a bug, but feel free to reply with further
questions or comments.

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

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