1) Read the help file

?timezones

and note that the R project does not do any of the programming associated with 
that functionality.

2) Keep in mind that it is you who are supplying an indeterminate value to be 
interpreted. You need to know from context (another column of data? The trend 
of values preceding this value?) whether this value should be interpreted as DT 
or ST. You would have to convert first to POSIXlt and fix the isdst value 
yourself for those values that need your attention before converting to POSIXct.

3) Please read the posting guide and follow it, including posting in plain text 
on this mailing list.
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Sent from my phone. Please excuse my brevity.

On January 19, 2015 3:51:39 AM PST, Vasantha Kumar Kesavan 
<info.vas...@gmail.com> wrote:
>Hi,
>
>Let me know, how to set/unset "isdst" parameter in system/session
>level.
>
>I could understand the possible values of isdst 0, 1 and -1.
>
>Example:
>
>Sys.setenv(TZ="PST8PDT");
>as.POSIXct("2007-11-04 01:00:00");
>
>when I was executed the above command,
>
>LINUX.X64 -> it was treated as PST value.
>[1] "2007-11-04 01:00:00 PST"
>
>WINDOWS.X64 -> it was treated as PDT value
>[1] "2007-11-04 01:00:00 PDT"
>
>SOLARIS.X64 -> it was treated as PST value.
>[1] "2007-11-04 01:00:00 PST"
>
>In 2007 the Daylight saving time was ended at 2007-11-04 02:00:00, so
>there
>was two "2007-11-04 01:00:00" values each for Standard and Daylight
>time.
>
>But I was not able to understand, how R is displaying the datetime as
>PST/PDT.
>
>Please do the needful.
>
>
>Thanks
>Vasanth
>
>       [[alternative HTML version deleted]]
>
>______________________________________________
>R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see
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>PLEASE do read the posting guide
>http://www.R-project.org/posting-guide.html
>and provide commented, minimal, self-contained, reproducible code.

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