[R] problem setting default timezone

Michael Dewey lists at dewey.myzen.co.uk
Thu Apr 23 15:23:56 CEST 2015

In-line below

On 23/04/2015 14:01, Bos, Roger wrote:
> Dear All,
> I would like to learn the proper way to set the default time zone so I get the correct date for my files.  The code below is non-reproducible (sorry) because it is based on a file on my system, but I hope someone will be able to help me anyway.
> I have a file that was last modified on 4/21/2015:
>> file.info("E:/snap/q/snap_q_q1_" %+% endPeriod %+% ".txt")$mtime
> [1] "2015-04-21 20:26:33 EDT"
> When I convert that to a date, I gives me 2015-04-22.  I read about timezones and saw that there are two possible places to set the default values: One as a system variable and one as an option.  To be safe I set both:
>>      Sys.setenv(TZ='America/New_York')
>>      Sys.getenv("TZ")
> [1] "America/New_York"
>>      options(tz='America/New_York')
>>      getOption("tz")
> [1] "America/New_York"
>>      as.Date(file.info("E:/snap/q/snap_q_q1_" %+% endPeriod %+% ".txt")$mtime)
> [1] "2015-04-22"
> But as you can see R still gives me the wrong date.  I can get the correct date as follows:
>>      as.Date(file.info("E:/snap/q/snap_q_q1_" %+% endPeriod %+% ".txt")$mtime, tz='America/New_York')
> [1] "2015-04-21"
> But my question is why is the as.Date function not using the timezone I have set?

Because it has a tz= parameter which sets its time zone. I think you 
need to write your own wrapper function to pick up your preferred timezone.

> Thank you in advance,
> Roger
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