title: ggplot2 and chron barplot of time data scale_x_chron
body: <p>I have a number of times and want to plot the frequency of each time in a barplot</p>
  
  <pre><code>library(ggplot2)
  library(chron)
  test &lt;- data.frame(times = c(rep("7:00:00",4), rep("8:00:00",3), 
                           rep("12:00:00",1), rep("13:00:00",5)))
  test$times &lt;- times(test$times)
  test
        times
  1  07:00:00
  2  07:00:00
  3  07:00:00
  4  07:00:00
  5  08:00:00
  6  08:00:00
  7  08:00:00
  8  12:00:00
  9  13:00:00
  10 13:00:00
  11 13:00:00
  12 13:00:00
  13 13:00:00
  </code></pre>
  
  <p>The value of <code>binwidth</code> is chosen to represent minutes</p>
  
  <pre><code>p &lt;- ggplot(test, aes(x = times)) + geom_bar(binwidth=1/24/60)
  p + scale_x_chron(format="%H:%M")
  </code></pre>
  
  <p>As you see the scales are plus one hour in the x-axis:</p>
  
  <p><a href="https://i.stack.imgur.com/ug4Ik.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/ug4Ik.png" alt="enter image description here"></a></p>
  
  <p>I have the feeling that is has something to do with the timezone, but I cant really place it:</p>
  
  <pre><code>Sys.timezone()
  [1] "CET"
  </code></pre>
  
  <p>Edit:
  Thanks @shadow for comment</p>
  
  <p>UPDATE:</p>
  
  <p>If I run <code>Sys.setenv(TZ='GMT')</code> first it works perfectly. The problem is in the <code>times()</code> function. I automatically sets the timezone to <code>GMT</code> and if I'm plotting the x-axis, ggplot notices that my system-timezone is <code>CET</code> and adds one hour on the plot. 
  Now if i'm setting my system-timezone to <code>GMT</code>, ggplot doesn't add an hour.</p>