On 21/09/2014 14:11, Denis Chabot wrote:
Hi,
I have to deal with time-stamped data coming from outside my own time zone, so
the problem is likely poor knowledge of European time zones on my part. But I
am puzzled just the same.
I thought that setting a time zone of "Europe/Copenhagen" would be the same as "CET" in
winter and "CEST" in summer.
You thought wrong: CEST is not a valid timezone on most (maybe all) R
platforms.
You failed to tell us the 'at a minimum' information required by the
posting guide. ?Sys.timezone says OlsonNames() tells you the timezone
names supported on your unstated platform, and ?as.POSIXct says
tz: A time zone specification to be used for the conversion, _if
one is required_. System-specific (see time zones), but ‘""’
is the current time zone, and ‘"GMT"’ is UTC (Universal Time,
Coordinated). Invalid values are most commonly treated as
UTC, on some platforms with a warning.
As the posting guide asks, please do your own homework.
This test in winter works as expected:
a = as.POSIXct("2013-02-25 01:00:00", tz="Europe/Copenhagen"); a
[1] "2013-02-25 01:00:00 CET"
b = as.POSIXct("2013-02-25 01:00:00", tz="CET"); b
[1] "2013-02-25 01:00:00 CET"
a-b
Time difference of 0 secs
But this one is summer does not work as I expected:
c = as.POSIXct("2013-07-25 01:00:00", tz="Europe/Copenhagen"); c
[1] "2013-07-25 01:00:00 CEST"
d = as.POSIXct("2013-07-25 01:00:00", tz="CEST"); d
[1] "2013-07-25 01:00:00 UTC"
e = as.POSIXct("2013-07-25 01:00:00", tz="CET"); e
[1] "2013-07-25 01:00:00 CEST"
c-d
Time difference of -2 hours
c-e
Time difference of 0 secs
Setting tz to "Europe/Copenhagen" in summer in c first appears to be the same as setting it to
"CEST" because the output is showing "CEST".
But d should then be the same as c, and it is not.
What is happening?
Thanks in advance,
Denis Chabot
______________________________________________
[email protected] mailing list
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.
--
Brian D. Ripley, [email protected]
Emeritus Professor of Applied Statistics, University of Oxford
1 South Parks Road, Oxford OX1 3TG, UK
______________________________________________
[email protected] mailing list
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.
