Timezone issue with strftime/strptime and %z and %Z

2011/3/11 David Winsemius <dwinsemius at comcast.net>:

On Mar 11, 2011, at 8:54 AM, Daniel N?st wrote:

Let me rephrase my question: How can I create a time object from the
character string "1995-05-25T15:30:00-10:00" and get exactly the  
same
character string again when formatting it/printing it?

x <- as.POSIXlt(gsub("T", " ", #change T to space

+           # but preserve the sign for the %z format string
+           gsub("(T..:..:.....):", "\\1",  
"1995-05-25T15:30:00-10:00")),
 format="%Y-%m-%d %H:%M:%S%z", tz="GMT")

x

[1] "1995-05-26 01:30:00 GMT"

format(x, "%Y-%m-%d %H:%M:%S%z")

[1] "1995-05-26 01:30:00+0000"

format(x, "%Y-%m-%dT%H:%M:%S%z")

[1] "1995-05-26T01:30:00+0000"

My output is:

format(x, "%Y-%m-%d %H:%M:%S%z")
# [1] "1995-05-26 03:30:00Mitteleurop?ische Zeit"
format(x, "%Y-%m-%dT%H:%M:%S%z")
# [1] "1995-05-26T01:30:00Mitteleurop?ische Zeit"

What are your locale settings?

The root of problem probably is my
German Windows, but I would think there is some way to fix that...

Sys.getlocale(category = "LC_TIME")

[1] "German_Germany.1252"

It is easy todeal with the "T" separator. You did say that the ":"  
was
optional in the output, didn't you?

Yes, I don't worry too much about the ":" (as I am contacting a web
service with that data it might actually accept it without).

Thanks,

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

David Winsemius, MD
West Hartford, CT

David Winsemius, MD
West Hartford, CT