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  a character vector of length 3 giving the timezone name from the
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  a character vector of length 3 giving the timezone name from the
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  \env{TZ} environment variable and the names of the base timezone
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  \env{TZ} environment variable and the names of the base timezone
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  and the alternate (daylight-saving) timezone.  Sometimes this may
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  and the alternate (daylight-saving) timezone.  Sometimes this may
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  just be of length one, giving the timezone name.
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  just be of length one, giving the timezone name.
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  \code{"POSIXct"} objects may also have an attribute \code{"tzone"}, a
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  character vector of length one.  If set, it will determine how the
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  object is converted to class \code{"POSIXlt"} and in particular how it
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  is printed.  This is usually desirable, but if you want to specify an
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  object in a particular timezone but to be printed in the current
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  timezone you may want to remove the \code{"tzone"} attribute (e.g. by
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  \code{c(x)}).
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  Unfortunately, the conversion is complicated by the operation of time
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  Unfortunately, the conversion is complicated by the operation of time
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  zones and leap seconds (22 days have been 86401 seconds long so far:
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  zones and leap seconds (22 days have been 86401 seconds long so far:
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  the times of the extra seconds are in the object \code{.leap.seconds}).
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  the times of the extra seconds are in the object \code{.leap.seconds}).
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  The details of this are entrusted to the OS services where possible.
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  The details of this are entrusted to the OS services where possible.
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  This will usually cover the period 1970--2037, and on Unix machines
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  This will usually cover the period 1970--2037, and on Unix machines
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  be wrong if the system has changed since build time, just possibly by
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  be wrong if the system has changed since build time, just possibly by
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  changing locales.)
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  changing locales.)
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  Using \code{\link{c}} on \code{"POSIXlt"} objects converts them to the
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  Using \code{\link{c}} on \code{"POSIXlt"} objects converts them to the
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  current time zone.
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  current time zone.
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}
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}
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\seealso{
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\seealso{
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  \code{\link{as.POSIXct}} and \code{\link{as.POSIXlt}} for conversion
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  \code{\link{as.POSIXct}} and \code{\link{as.POSIXlt}} for conversion
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  between the classes.
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  between the classes.
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Sys.time() - 3600             # an hour ago
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Sys.time() - 3600             # an hour ago
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as.POSIXlt(Sys.time(), "GMT") # the current time in GMT
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as.POSIXlt(Sys.time(), "GMT") # the current time in GMT
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format(.leap.seconds)         # all 22 leapseconds in your timezone
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format(.leap.seconds)         # all 22 leapseconds in your timezone
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print(.leap.seconds, tz="PST8PDT")  # and in Seattle's
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}
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}
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\keyword{utilities}
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\keyword{utilities}
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\keyword{chron}
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\keyword{chron}