title: R lubridate converting seconds to date
body: <p>I have a simple question regarding R's lubridate package. I've a series of timestamps in seconds since epoch. I want to convert this to YYYY-MM-DD-HH format. In base R, I can do something like this to first convert it to a date format</p>
  
  <pre><code>&gt; x = as.POSIXct(1356129107,origin = "1970-01-01",tz = "GMT")
  &gt; x
  [1] "2012-12-21 22:31:47 GMT"
  </code></pre>
  
  <p>Note the above just converts it to a date format, not the YYYY-MM-DD-HH format. How would I do this in lubridate? How would I do it using base R?</p>
  
  <p>Thanks much in advance</p>