title: R timestamp difference printing
body: <p>In below code, the last and the second last R codes produce a bit different result, why? After running the last line why don't I get output "time difference is Time difference of 5 mins"?
  how could I get such output?</p>
  
  <pre><code>filenames &lt;- c("CH7Data_20130401T130110.csv", "CH7Data_20130401T130610.csv")
  timestamps &lt;- gsub(".*_([^.]+).*", "\\1", filenames)
  ## [1] "20130401T130110" "20130401T130610"
  timestamps &lt;- as.POSIXlt(timestamps, format = "%Y%m%dT%H%M%S")
  ## [1] "2013-04-01 13:01:10 PDT" "2013-04-01 13:06:10 PDT"
  timestamps[2]-timestamps[1]
  ##Time difference of 5 mins
  cat("time difference is",timestamps[2]-timestamps[1])
  ##time difference is 5
  </code></pre>