[R] Date Time, as.POSIXct used locale, strange plot behavior

[Tilmann Faul]

Dear Jeff,

Thanks for your answer.
Sys.timezone()  gives
[1] "Europe/Berlin"
I tried "Europe/Berlin" as tz argument, giving the same result als using
"CEST" (Central European Summer Time).
It seems to me, that using as.POSIXct without tz argument defaults to tz
UTC and with tz argument, either "CEST" or "Europ/Berlin" uses the
European tz, regarding the plot.
Never the less i do not understand why all of them have the same time
printout on my system.

as.POSIXct("2021-04-21 00:00:00", tz="CEST")
# [1] "2021-04-21 CEST"
as.POSIXct("2021-04-21 00:00:00", tz="Europ/Berlin")
# [1] "2021-04-21 Europ"
as.POSIXct("2021-04-21 00:00:00")
# [1] "2021-04-21 CEST"

Can someone comment on that, please?

best Regards
Tilmann

On 29.04.21 23:19, Jeff Newmiller wrote:
> What is your TZ environment variable set to? That's what time conversion defaults to  ?DateTimeClasses
> 
> Also, I am not sure CEST is a valid timezone designation... it can be system dependent, but using one of the elements listed in ?OlsonNames.
> 
> On April 29, 2021 12:22:44 PM PDT, Tilmann Faul <Tilmann_Faul using t-online.de> wrote:
>> Hy,
>>
>> stumbled over the following problem while plotting DateTime Objects.
>>
>> plot(as.POSIXct(c("2021-04-21 00:00:00", "2021-04-21 23:59:59")), c(0,
>> 1), type='l')
>>
>> arrows(as.POSIXct("2021-04-21 00:00:00", tz="CEST"),
>>       0.3,
>>       as.POSIXct("2021-04-21 00:00:00", tz="CEST"),
>>       0.2,
>>       length=0.07, angle=15)
>>
>> # arrow at 02:00, why?
>>
>> arrows(as.POSIXct("2021-04-21 00:00:00"),
>>       0.3,
>>       as.POSIXct("2021-04-21 00:00:00"),
>>       0.2,
>>       length=0.07, angle=15, col='red')
>>
>> # arrow at 00:00 as expected
>>
>> as.POSIXct(c("2021-04-21 00:00:00", "2021-04-21 23:59:59"))[1]
>> # [1] "2021-04-21 CEST"
>> as.POSIXct("2021-04-21 00:00:00", tz="CEST")
>> # [1] "2021-04-21 CEST"
>> as.POSIXct("2021-04-21 00:00:00")
>> # [1] "2021-04-21 CEST"
>>
>> all representations on my system are the same, why is the plot location
>> of the arrows different??
>> I am located in Germany, my locale:
>> Sys.getlocale()
>> [1]
>> "LC_CTYPE=de_DE.UTF-8;LC_NUMERIC=C;LC_TIME=de_DE.UTF-8;LC_COLLATE=de_DE.UTF-8;LC_MONETARY=de_DE.UTF-8;LC_MESSAGES=de_DE.UTF-8;LC_PAPER=de_DE.UTF-8;LC_NAME=C;LC_ADDRESS=C;LC_TELEPHONE=C;LC_MEASUREMENT=de_DE.UTF-8;LC_IDENTIFICATION=C"
>>
>> Any Idea?
>>
>> Best regards
>> Tilmann
>>
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>