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A general description is here.
‘file.copy()’ gains a ‘copy.date’ argument.
There is more support to explore the system's idea of time-zone names. ‘Sys.timezone()’ tries to give the current system setting (and succeeds at least on Linux, OS X, Solaris and Windows), and ‘OlsonNames()’ lists the names in the system's Olson database. ‘Sys.timezone(location = FALSE)’ gives the previous behaviour.
On a Unix-alike ‘Sys.timezone()’ returns ‘NA’ if the environment variable ‘TZ’ is unset, to distinguish it from an empty string which on some OSes means the ‘UTC’ time zone.