[Rd] [R] R-3.4.0 fails test

Martin Maechler maechler at stat.math.ethz.ch
Thu May 18 17:46:08 CEST 2017

> > On 18 May 2017, at 14:58 , Martyn Plummer <plummerM at iarc.fr> wrote:
> > 
> >> On 18 May 2017, at 14:51, peter dalgaard <pdalgd at gmail.com> wrote:

> >>> On 18 May 2017, at 13:47 , Joris Meys <jorismeys at gmail.com> wrote:
> >>> 
> >>> Correction: Also dlt uses the default timezone, but POSIXlt is not recalculated whereas POSIXct is. Reason for that is the different way values are stored (hours, minutes, seconds as opposed to minutes from origin, as explained in my previous mail)
> >>> 
> >> 
> >> I would suspect that there is something more subtle going on, New Zealand time is 10, 11, or 12 hours from Central European, depending on time of year (10 in our Summer, 12 in theirs and 11 during the overlap at both ends, if you must know), and we are talking a 1 hour difference.  
> >> 
> >> However DST transitions were both in March/April, so that's not it. Maybe a POSIX[lc]t expert can comment?
> > 
> > If I change the month from December to June then I see the same phenomenon in my Europe/Paris time zone. The issue seems to be that, for the date chosen for the test, Summer/daylight savings time is in force in NZ and some other parts of the southern hemisphere , but not in the northern hemisphere.
> > 

> Of course! I overlooked that the date in the test is the issue, not the current date. (Let's blame that on the fact that Summer seems to have finally arrived in Copenhagen...)

> "svn praise" claims this test is due to Martin Maechler in r71742, so maybe he knows how to fix it. (I wonder if he just used the current date at the time, or actually thought that there would be no DST issues in December ;-) )

> -pd

I think the former.  This was about fixing a segmentation fault problem
 (thread from Dec 6, 2016, on the R-devel mailing list, starting
  here: https://stat.ethz.ch/pipermail/r-devel/2016-December/073448.html )
mostly,  but the 2nd part of the regression test evidently needs
more thought than I had put there.

Being pretty "stretched" time wise currently, I'm happy for
timezone-portable propositions to change the test.


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