[debbugs-tracker] bug#26165: closed (date-week-day screws up prior to AD 1)

[GNU bug Tracking System]

Your message dated Sun, 21 Oct 2018 16:41:06 -0400
with message-id <address@hidden>
and subject line Re: bug#26165: date-week-day screws up prior to AD 1
has caused the debbugs.gnu.org bug report #26165,
regarding date-week-day screws up prior to AD 1
to be marked as done.

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-- 
26165: http://debbugs.gnu.org/cgi/bugreport.cgi?bug=26165
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> --- Begin Message ---
>
>
>
> Subject: 
>
> date-week-day screws up prior to AD 1
>
>
>
>
> Date: 
>
> Sat, 18 Mar 2017 23:45:28 +0000
>
>
>
>
> Looking at day of the week, via SRFI-19's date-week-day:
>
> scheme@(guile-user)> (use-modules (srfi srfi-19))
> scheme@(guile-user)> (julian-day->date 1721426 0) 
> $1 = #<date nanosecond: 0 second: 0 minute: 0 hour: 12 day: 1 month: 1 year: 1 
> zone-offset: 0>
> scheme@(guile-user)> (date-week-day (julian-day->date 1721426 0))
> $2 = 1
> scheme@(guile-user)> (date-week-day (julian-day->date 1721425 0))
> $3 = 6
>
> The output for 0001-01-01, Monday, is correct.  The preceding day is
> actually a Sunday, but Saturday was shown.  Looking at the code, this
> bug arises for the same reason as the problem with date-year-day raised
> in bug#26151.  The date-year value, of the weird zero-skipping year
> numbering, is passed to an algorithm that obviously expects astronomical
> year numbering.
>
> Looking at the code also reveals a second problem: the algorithm is
> written to perform divisions with quotient where it obviously needs
> modulo.  This will manifest in erroneous computations for some earlier
> years once the above is fixed.
>
> -zefram
>
>
>
> --- End Message ---
> --- Begin Message ---
>
>
>
> Subject: 
>
> Re: bug#26165: date-week-day screws up prior to AD 1
>
>
>
>
> Date: 
>
> Sun, 21 Oct 2018 16:41:06 -0400
>
>
>
>
> User-agent: 
>
> Gnus/5.13 (Gnus v5.13) Emacs/26.1 (gnu/linux)
>
>
>
>
> Zefram <address@hidden> writes:
>
> > Looking at day of the week, via SRFI-19's date-week-day:
> >
> > scheme@(guile-user)> (use-modules (srfi srfi-19))
> > scheme@(guile-user)> (julian-day->date 1721426 0) 
> > $1 = #<date nanosecond: 0 second: 0 minute: 0 hour: 12 day: 1 month: 1 year: 
> > 1 zone-offset: 0>
> > scheme@(guile-user)> (date-week-day (julian-day->date 1721426 0))
> > $2 = 1
> > scheme@(guile-user)> (date-week-day (julian-day->date 1721425 0))
> > $3 = 6
> >
> > The output for 0001-01-01, Monday, is correct.  The preceding day is
> > actually a Sunday, but Saturday was shown.  Looking at the code, this
> > bug arises for the same reason as the problem with date-year-day raised
> > in bug#26151.
>
> This is fixed by commit a58c7abd72648f77e4ede5f62a2c4e7969bb7f95 on the
> stable-2.2 branch.  I'm closing this bug now, but please reopen if
> appropriate.
>
>      Thanks!
>        Mark
>
>
> --- End Message ---