title: Format Date from Offset to Greenwich to standard time in R
body: <p>I am currently looking at some data I uploaded from the EPA website but the date is formatted a little funny: 20170101T2300-0500
  I tried reformatting the date and time at once which did not work so I split the column by "T" and successfully reformatted the date but when I entered </p>
  
  <pre><code>Df$time&lt;-strptime(as.character(Df$time),"%I%M%z")
  Df$time&lt;- format(Df$time, "%I:%M:%S")
  </code></pre>
  
  <p>The time column turned into N/A's. I read that "z" was the "offset to Greenwich" factor but for output only, I'm unsure if I used it in the correct context. </p>