R help - Mar 2011 - Timezone issue with strftime/strptime and %z and %Z

Hello!

I've been trying to get this right for quite a while now and fear
there is an easy solution I just don't see. I did not have this
problem in Linux, and I searched r-help and Google but did not find a
solution, but of course I am grateful for and resources I might not
have found our not understood yet.

I try to parse a time stamp with time zone. I essentially just want to
parse the time stamp "1995-05-25T15:30:00+10:00" and output it exactly
like it is, using the POSIX classes (or is that impossible?).

Please find the script and output/comments below.

Regards,
Daniel

> sessionInfo()
R version 2.12.1 (2010-12-16)
Platform: x86_64-pc-mingw32/x64 (64-bit)

locale:
[1] LC_COLLATE=German_Germany.1252  LC_CTYPE=German_Germany.1252
[3] LC_MONETARY=German_Germany.1252 LC_NUMERIC=C
[5] LC_TIME=German_Germany.1252

attached base packages:
[1] stats     graphics  grDevices utils     datasets  methods   base

other attached packages:
[1] rj_0.5.2-1

loaded via a namespace (and not attached):
[1] rJava_0.8-8  tools_2.12.1
>
> t1 <- strptime("1995-05-25T15:30:00+10:00", format =
"%Y-%m-%dT%H:%M:%OS")
> t2 <- strptime("1995-05-25T15:30:00+10:00", format =
"%Y-%m-%dT%H:%M:%OS%z")
>
> strftime(t1, format = "%Y-%m-%dT%H:%M:%OS")
[1] "1995-05-25T15:30:00"
> strftime(t1, format = "%Y-%m-%dT%H:%M:%OS%z")
[1] "1995-05-25T15:30:00Mitteleurop?ische
Sommerzeit"
> # Ends in "Mitteleurop?ische Sommerzeit", not in +10:00, so time
zone is ignored!
> # Also no difference beetween %z and %z !
> strftime(t1, format = "%Y-%m-%dT%H:%M:%OS%Z")
[1] "1995-05-25T15:30:00Mitteleurop?ische
Sommerzeit"
> # All this does NOT remove the "Mitteleurop?ische Zeit" from the
strftime output!!
>
> # Can locale solve the problem?
> Sys.getlocale(category = "LC_TIME")
[1] "German_Germany.1252"
> Sys.setlocale("LC_TIME", "English")
[1] "English_United States.1252"
>
> strftime(t1, format = "%Y-%m-%dT%H:%M:%OS%z")
[1] "1995-05-25T15:30:00Mitteleurop?ische
Sommerzeit"
> # [1] "1995-05-25T15:30:00Mitteleurop?ische Sommerzeit" -- No
change.
>
> # does t1 actually have time zone?
> attributes(t1)
$names
[1] "sec"   "min"   "hour"  "mday" 
"mon"   "year"  "wday"  "yday" 
"isdst"

$class
[1] "POSIXlt" "POSIXt"
>
> format(t1, format = "%Y-%m-%dT%H:%M:%OS%z") # usetz = TRUE) # no
change on usetz
[1] "1995-05-25T15:30:00Mitteleurop?ische
Sommerzeit"
>
> # Is the : in offset the problem?
> t3 <- strptime("1995-05-25T15:30:00+1000", format =
"%Y-%m-%dT%H:%M:%S%z")
> attributes(t3)
$names
[1] "sec"   "min"   "hour"  "mday" 
"mon"   "year"  "wday"  "yday" 
"isdst"

$class
[1] "POSIXlt" "POSIXt"
> format(t3, format = "%Y-%m-%dT%H:%M:%OS%z")
[1] "1995-05-25T07:30:00Mitteleurop?ische
Sommerzeit"
> # [1] "1995-05-25T07:30:00Mitteleurop?ische Sommerzeit"
>
> strftime(t1, format = "%Y-%m-%dT%H:%M:%OS%z", tz =
"+0200") # no effect on setting tz
[1] "1995-05-25T15:30:00Mitteleurop?ische
Sommerzeit"
>
> Sys.setenv(TZ="GMT") # no working effect on format and strftime

On Mar 10, 2011, at 11:17 AM, Daniel N?st wrote:
> Hello!
>
> I've been trying to get this right for quite a while now and fear
> there is an easy solution I just don't see. I did not have this
> problem in Linux, and I searched r-help and Google but did not find a
> solution, but of course I am grateful for and resources I might not
> have found our not understood yet.
>
> I try to parse a time stamp with time zone. I essentially just want to
> parse the time stamp "1995-05-25T15:30:00+10:00" and output it
exactly
> like it is, using the POSIX classes (or is that impossible?).
Does this work?

as.POSIXlt(gsub("T.*(\\+|\\-)..(:)", "", # get rid of the
colon in the
tz
            # but preserve the sign for the %z format string
            gsub("T", " ",
"1995-05-25T15:30:00-1000")), # replace the
"T" with a space
             format="%Y-%m-%d %H:%M:%S%z")
>
> Please find the script and output/comments below.
>
> Regards,
> Daniel
>
>
>> sessionInfo()
> R version 2.12.1 (2010-12-16)
> Platform: x86_64-pc-mingw32/x64 (64-bit)
>
> locale:
> [1] LC_COLLATE=German_Germany.1252  LC_CTYPE=German_Germany.1252
> [3] LC_MONETARY=German_Germany.1252 LC_NUMERIC=C
> [5] LC_TIME=German_Germany.1252
>
> attached base packages:
> [1] stats     graphics  grDevices utils     datasets  methods   base
>
> other attached packages:
> [1] rj_0.5.2-1
>
> loaded via a namespace (and not attached):
> [1] rJava_0.8-8  tools_2.12.1
>>
>> t1 <- strptime("1995-05-25T15:30:00+10:00", format =
"%Y-%m-%dT%H:
>> %M:%OS")
>> t2 <- strptime("1995-05-25T15:30:00+10:00", format =
"%Y-%m-%dT%H:
>> %M:%OS%z")
>>
>> strftime(t1, format = "%Y-%m-%dT%H:%M:%OS")
> [1] "1995-05-25T15:30:00"
>> strftime(t1, format = "%Y-%m-%dT%H:%M:%OS%z")
> [1] "1995-05-25T15:30:00Mitteleurop?ische Sommerzeit"
>> # Ends in "Mitteleurop?ische Sommerzeit", not in +10:00, so
time
>> zone is ignored!
>> # Also no difference beetween %z and %z !
>> strftime(t1, format = "%Y-%m-%dT%H:%M:%OS%Z")
> [1] "1995-05-25T15:30:00Mitteleurop?ische Sommerzeit"
>> # All this does NOT remove the "Mitteleurop?ische Zeit" from
the
>> strftime output!!
>>
>> # Can locale solve the problem?
>> Sys.getlocale(category = "LC_TIME")
> [1] "German_Germany.1252"
>> Sys.setlocale("LC_TIME", "English")
> [1] "English_United States.1252"
>>
>> strftime(t1, format = "%Y-%m-%dT%H:%M:%OS%z")
> [1] "1995-05-25T15:30:00Mitteleurop?ische Sommerzeit"
>> # [1] "1995-05-25T15:30:00Mitteleurop?ische Sommerzeit" -- No
change.
>>
>> # does t1 actually have time zone?
>> attributes(t1)
> $names
> [1] "sec"   "min"   "hour"  "mday" 
"mon"   "year"  "wday"  "yday"
> "isdst"
>
> $class
> [1] "POSIXlt" "POSIXt"
>
>>
>> format(t1, format = "%Y-%m-%dT%H:%M:%OS%z") # usetz = TRUE) #
no
>> change on usetz
> [1] "1995-05-25T15:30:00Mitteleurop?ische Sommerzeit"
>>
>> # Is the : in offset the problem?
>> t3 <- strptime("1995-05-25T15:30:00+1000", format =
"%Y-%m-%dT%H:%M:
>> %S%z")
>> attributes(t3)
> $names
> [1] "sec"   "min"   "hour"  "mday" 
"mon"   "year"  "wday"  "yday"
> "isdst"
>
> $class
> [1] "POSIXlt" "POSIXt"
>
>> format(t3, format = "%Y-%m-%dT%H:%M:%OS%z")
> [1] "1995-05-25T07:30:00Mitteleurop?ische Sommerzeit"
>> # [1] "1995-05-25T07:30:00Mitteleurop?ische Sommerzeit"
>>
>> strftime(t1, format = "%Y-%m-%dT%H:%M:%OS%z", tz =
"+0200") # no
>> effect on setting tz
> [1] "1995-05-25T15:30:00Mitteleurop?ische Sommerzeit"
>>
>> Sys.setenv(TZ="GMT") # no working effect on format and
strftime
>
-- 

David Winsemius, MD
West Hartford, CT