> On 18 May 2017, at 14:51, peter dalgaard <pda...@gmail.com> wrote:
>
>
>> On 18 May 2017, at 13:47 , Joris Meys <jorism...@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.
Martyn
> -pd
>
>> CHeers
>> Joris
>>
>> On Thu, May 18, 2017 at 1:45 PM, Joris Meys <jorism...@gmail.com> wrote:
>> This has to do with your own timezone. If I run that code on my computer,
>> both formats are correct. If I do this after
>>
>> Sys.setenv(TZ = "UTC")
>>
>> Then:
>>
>>> cbind(format(dlt), format(dct))
>> [,1] [,2]
>> [1,] "2016-12-06 21:45:41" "2016-12-06 20:45:41"
>> [2,] "2016-12-06 21:45:42" "2016-12-06 20:45:42"
>>
>> The reason for that, is that dlt has a timezone set, but dct doesn't. To be
>> correct, it only takes the first value "", which indicates "Use the default
>> timezone of the locale".
>>
>>> attr(dlt, "tzone")
>> [1] "" "CET" "CEST"
>>> attr(dct, "tzone")
>> [1] ""
>>
>> The thing is, in POSIXlt the timezone attribute is stored together with the
>> actual values for hour, minute etc. in list format. Changing the timezone
>> doesn't change those values, but it will change the time itself:
>>
>>> Sys.unsetenv("TZ")
>>> dlt2 <- dlt
>>> attr(dlt2,"tzone") <- "UTC"
>>> dlt2
>> [1] "2016-12-06 21:45:41 UTC" "2016-12-06 21:45:42 UTC"
>> [3] "2016-12-06 21:45:43 UTC" "2016-12-06 21:45:44 UTC"
>>
>> in POSIXct the value doesn't change either, just the attribute. But this
>> value is the number of seconds since the origin. So the time itself doesn't
>> change, but you'll see a different hour.
>>
>>> dct
>> [1] "2016-12-06 21:45:41 CET" "2016-12-06 21:45:42 CET"
>> ...
>>> attr(dct,"tzone") <- "UTC"
>>> dct
>> [1] "2016-12-06 20:45:41 UTC" "2016-12-06 20:45:42 UTC"
>> [3] "2016-12-06 20:45:43 UTC" "2016-12-06 20:45:44 UTC"
>>
>> So what you see, is simply the result of your timezone settings on your
>> computer.
>>
>> Cheers
>> Joris
>>
>>> On Thu, May 18, 2017 at 1:19 PM, peter dalgaard <pda...@gmail.com> wrote:
>>>
>>> On 18 May 2017, at 11:00 , Patrick Connolly <p_conno...@slingshot.co.nz>
>>> wrote:
>>>
>>> On Wed, 17-May-2017 at 01:21PM +0200, Peter Dalgaard wrote:
>>>
>>> |>
>>> |> Anyways, you might want to
>>> |>
>>> |> a) move the discussion to R-devel
>>> |> b) include your platform (hardware, OS) and time zone info
>>>
>>> System: Host: MTA-V1-427894 Kernel: 3.19.0-32-generic x86_64 (64 bit
>>> gcc: 4.8.2)
>>> Desktop: KDE Plasma 4.14.2 (Qt 4.8.6) Distro: Linux Mint 17.3 Rosa
>>
>> I suppose that'll do...
>>
>>
>>> Time zone: NZST
>>
>>
>>
>>>
>>> |> c) run the offending code lines "by hand" and show us the values of
>>> format(dlt) and format(dct) so we can see what the problem is, something
>>> like
>>> |>
>>> |> dlt <- structure(
>>> |> list(sec = 52, min = 59L, hour = 18L, mday = 6L, mon = 11L, year =
>>> 116L,
>>> |> wday = 2L, yday = 340L, isdst = 0L, zone = "CET", gmtoff = 3600L),
>>> |> class = c("POSIXlt", "POSIXt"), tzone = c("", "CET", "CEST"))
>>> |> dlt$sec <- 10000 + 1:10
>>> |> dct <- as.POSIXct(dlt)
>>> |> cbind(format(dlt), format(dct))
>>>
>>>> cbind(format(dlt), format(dct))
>>> [,1] [,2]
>>> [1,] "2016-12-06 21:45:41" "2016-12-06 22:45:41"
>>> [2,] "2016-12-06 21:45:42" "2016-12-06 22:45:42"
>>> [3,] "2016-12-06 21:45:43" "2016-12-06 22:45:43"
>>> [4,] "2016-12-06 21:45:44" "2016-12-06 22:45:44"
>>> [5,] "2016-12-06 21:45:45" "2016-12-06 22:45:45"
>>> [6,] "2016-12-06 21:45:46" "2016-12-06 22:45:46"
>>> [7,] "2016-12-06 21:45:47" "2016-12-06 22:45:47"
>>> [8,] "2016-12-06 21:45:48" "2016-12-06 22:45:48"
>>> [9,] "2016-12-06 21:45:49" "2016-12-06 22:45:49"
>>> [10,] "2016-12-06 21:45:50" "2016-12-06 22:45:50"
>>>>
>>>
>>
>>
>> So exactly 1 hour out of whack. Is there a Daylight Saving Times issue,
>> perchance?
>>
>> -pd
>>
>>
>>>
>>> --
>>> ~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.
>>> ___ Patrick Connolly
>>> {~._.~} Great minds discuss ideas
>>> _( Y )_ Average minds discuss events
>>> (:_~*~_:) Small minds discuss people
>>> (_)-(_) ..... Eleanor Roosevelt
>>>
>>> ~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.
>>
>> --
>> Peter Dalgaard, Professor,
>> Center for Statistics, Copenhagen Business School
>> Solbjerg Plads 3, 2000 Frederiksberg, Denmark
>> Phone: (+45)38153501
>> Office: A 4.23
>> Email: pd....@cbs.dk Priv: pda...@gmail.com
>>
>> ______________________________________________
>> R-devel@r-project.org mailing list
>> https://stat.ethz.ch/mailman/listinfo/r-devel
>>
>>
>>
>> --
>> Joris Meys
>> Statistical consultant
>>
>> Ghent University
>> Faculty of Bioscience Engineering
>> Department of Mathematical Modelling, Statistics and Bio-Informatics
>>
>> tel : +32 (0)9 264 61 79
>> joris.m...@ugent.be
>> -------------------------------
>> Disclaimer : http://helpdesk.ugent.be/e-maildisclaimer.php
>>
>>
>>
>> --
>> Joris Meys
>> Statistical consultant
>>
>> Ghent University
>> Faculty of Bioscience Engineering
>> Department of Mathematical Modelling, Statistics and Bio-Informatics
>>
>> tel : +32 (0)9 264 61 79
>> joris.m...@ugent.be
>> -------------------------------
>> Disclaimer : http://helpdesk.ugent.be/e-maildisclaimer.php
>
> --
> Peter Dalgaard, Professor,
> Center for Statistics, Copenhagen Business School
> Solbjerg Plads 3, 2000 Frederiksberg, Denmark
> Phone: (+45)38153501
> Office: A 4.23
> Email: pd....@cbs.dk Priv: pda...@gmail.com
>
> ______________________________________________
> R-devel@r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-devel
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