[R] problem setting default timezone

[Bos, Roger]

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?

Thank you in advance,
Roger


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