R does a poor job of supporting timezone-specific objects... you have to
transfer the necessary attributes explicitly for many operations. (It does no
job of supporting element-specific timezones so don't go there.)
The good news is that R is pretty good at working with points in time, since
the default behavior of implementing time with numeric values in GMT always
means you can specify whatever timezone you want input or output to use, and
the timestamps are always ordered correctly in time.
I find that using the default empty string for tz attributes on POSIXt objects
(meaning use whatever is default) and letting the TZ environment variable
control the "current default" timezone is the most effective way to avoid
frustration with this. Don't hesitate to change that variable when you need to
convert to or from character or POSIXlt..
Sys.setenv( TZ="Etc/GMT+5" ) # read ?Olson
x <- as.POSIXct( "2017-03-31 19:00:00" )
Sys.setenv( TZ="Etc/GMT+8" )
y <- as.POSIXct( "2017-03-31 16:00:00" )
Sys.setenv( TZ="GMT" )
print( x )
print( y )
--
Sent from my phone. Please excuse my brevity.
On April 7, 2017 12:00:52 AM PDT, Troels Ring <tr...@gvdnet.dk> wrote:
>Thanks a lot - perhaps it is just understanding how times dates are
>handled, sorry to bother if that is just the case
>
>C[1]==A[1] # TRUE
>
>but
>
>C[1]
>[1] "2013-03-28 07:00:00 CET"
>A[1]
>[1] "2013-03-28 06:00:00 UTC"
>
>
>
>
>
>Den 07-04-2017 kl. 08:27 skrev Ulrik Stervbo:
>> Hi Troels,
>>
>> I get no error. I think we need more information to be of any help.
>>
>> Best wishes,
>> Ulrik
>>
>> On Fri, 7 Apr 2017 at 08:17 Troels Ring <tr...@gvdnet.dk> wrote:
>>
>>> Dear friends - I have further problems handling dates_times, as
>>> demonstrated below where concatenating two formatted vectors of
>>> date_times results in errors.
>>> I wonder why this happens and what was wrong in trying to take these
>two
>>> vectors together
>>> All best wishes
>>> Troels Ring
>>> Aalborg, Denmark
>>> Windows
>>> R version 3.3.2 (2016-10-31)
>>>
>>>
>>> A <- structure(c(1364450400, 1364450400, 1364536800, 1364623200,
>>> 1364709600,
>>> 1364796000, 1364882400, 1364968800, 1365055200, 1365141600,
>1365228000,
>>> 1365314400, 1365400800), class = c("POSIXct", "POSIXt"), tzone =
>"UTC")
>>> A
>>> B <- structure(c(1365141600, 1365228000, 1365314400, 1365400800,
>>> 1365487200,
>>> 1365573600, 1365660000, 1365746400, 1365832800, 1365919200,
>1366005600,
>>> 1366092000), class = c("POSIXct", "POSIXt"), tzone = "UTC")
>>> B
>>> C <- c(A,B)
>>> C
>>>
>>> ______________________________________________
>>> R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see
>>> https://stat.ethz.ch/mailman/listinfo/r-help
>>> PLEASE do read the posting guide
>>> http://www.R-project.org/posting-guide.html
>>> and provide commented, minimal, self-contained, reproducible code.
>>>
>> [[alternative HTML version deleted]]
>>
>> ______________________________________________
>> R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see
>> https://stat.ethz.ch/mailman/listinfo/r-help
>> PLEASE do read the posting guide
>http://www.R-project.org/posting-guide.html
>> and provide commented, minimal, self-contained, reproducible code.
>>
>
>______________________________________________
>R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see
>https://stat.ethz.ch/mailman/listinfo/r-help
>PLEASE do read the posting guide
>http://www.R-project.org/posting-guide.html
>and provide commented, minimal, self-contained, reproducible code.
______________________________________________
R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
