[R] Extent of time zone vulerability for POSIX date and time classes
timb at metrumrg.com
Thu Apr 5 18:15:09 CEST 2007
thanks for the feedback. I like the idea of coercing the system time
zone, and sticking with strptime/strftime. The balance would probably
tip in favor of chron, however, if I could get the format correct.
Apparently the default is two-digit year:
But I need four digit year, so I try:
Now, month has switched to character! I don't know of a format
convention that gets it back to numeric (although conventions are
documented for forcing to character). Comment?
Gabor Grothendieck wrote:
> If you use
> Sys.putenv(TZ = "GMT")
> at the beginning of your session then local time zone and GMT time
> zone will be the same so you should not have a problem. This was
> not possible, at least on Windows, at the time the R News article
> was written.
> On 4/5/07, Tim Bergsma <timb at metrumrg.com> wrote:
>> I frequently convert date and time data to and from character
>> representations. I'm frustrated with chron, because 'seconds' are
>> required to create a time object (my input data never has seconds).
> You could use paste:
> times(paste("12:30", 0, sep = ":"))
> and make it into a function if you use it a lot.
>> More importantly, I cannot make chron print the format 12/30/2006 (which
>> my output data requires).
> That is the default output format so you don't have to specify anything.
> only with POSIX that its not the default. For example:
>> x <- chron("12/30/2006")
>  12/30/06
>> I really like the format flexibility of strftime() and strptime(), but
>> of course am paranoid about timezone issues. After reading the standard
>> reference several times
>> (http://cran.r-project.org/doc/Rnews/Rnews_2004-1.pdf), I am tempted to
>> conclude that if I never specify timezones, and never use Sys.time(),
>> the vulnerabilities do not pertain.
> That won't protect you but this would let you use POSIX safely:
>> To the point: if I'm merely converting to and from character data that
>> does not represent time zones, is there still a time zone vulnerability
>> with strftime() and strptime()?
>> Thanks in advance,
>> Tim Bergsma, PhD
>> Metrum Research Group, LLC
>> "30-Dec-06 23:30",
>> format="%d-%b-%y %H:%M"
>> format="%m/%d/%Y %H:%M"
>>  "12/30/2006 23:30"
>> R-help at stat.math.ethz.ch mailing list
>> PLEASE do read the posting guide
>> and provide commented, minimal, self-contained, reproducible code.
More information about the R-help