title: Julia - strange joinpath() behaviour
body: <p>This is supposed to prefix the given path:</p>
  
  <pre><code>date = Date(2016, 6, 3)
  const FILEDATE_FORMAT = "YYYYmmdd"
  const FILE_PATH_FORMAT = "/YYYY/mm/"
  
  joinpath(
   "path-prefix",
    Dates.format(DateTime(date), FILE_PATH_FORMAT),
    Dates.format(DateTime(date), FILEDATE_FORMAT)
  )
  </code></pre>
  
  <p>Expected: <code>"/path-prefix/2016/06/20160603"</code></p>
  
  <p>Actual:   <code>"/2016/06/20160603"</code></p>
  
  <p>What is wrong here?</p>