Sys.setFileTime(path, time)"POSIXct" or an object which can
be coerced to one. Fractions of a second are ignored (prior to R 3.4.0).
utimes if that is
available, otherwise utime. On a POSIX file system it sets
both the last-access and modification times. On Windows it uses the system call SetFileTime to set the
‘last write time’. Some Windows file systems only record the
time at a resolution of two seconds.