title: Gnuplot: multiple lables on x axis
body: <p>I'm trying to plot the following data</p>
  
  <pre><code>29.07.2012 18:45:04;23.6;54
  29.07.2012 18:50:04;22.7;56
  29.07.2012 18:55:04;22.2;56
  29.07.2012 19:00:04;22.0;56
  29.07.2012 19:05:04;21.9;57
  29.07.2012 19:10:04;21.8;56
  29.07.2012 19:15:04;21.8;54
  29.07.2012 19:20:04;21.7;53
  29.07.2012 19:25:04;21.7;53
  </code></pre>
  
  <p>(Date, time, temperature, humidity) in the following style (cropped at the top):
  <a href="https://i.stack.imgur.com/kl0ID.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/kl0ID.png" alt="enter image description here"></a></p>
  
  <p>The labels on the x axis are the hour from the time of day and below are the weekdays and the date. I don't have the weekdays in my data file, but I'd like to have the date below the hours.</p>
  
  <p>My plotfile:</p>
  
  <pre><code>set datafile separator ";"
  set terminal png size 5280,1024
  set output '~/tfd.png'
  set xdata time
  set timefmt "%d.%m.%Y %H:%M:%S"
  set format x "%H"
  plot "data.csv" using 1:2 title 'temperatur'
  </code></pre>