[R] problems in vectors of dates_times

[William Michels]

I believe the lubridate package does a good job with time zones.

> install.packages("lubridate")
> library(lubridate)


Look at the supplied functions  with_tz()  and  force_tz().

HTH,

Bill.

William J. Michels, Ph.D.



On Fri, Apr 7, 2017 at 12:52 AM, Jeff Newmiller
<jdnewmil at dcn.davis.ca.us> wrote:
> 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 <tring at 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 <tring at 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 at 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 at r-project.org mailing list -- To UNSUBSCRIBE and more, see
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>>> PLEASE do read the posting guide
>>http://www.R-project.org/posting-guide.html
>>> and provide commented, minimal, self-contained, reproducible code.
>>>
>>
>>______________________________________________
>>R-help at 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 at 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.