title: gnuplot v4.4: Problem plotting using timeseries x axis
body: <p>could someone please help me. I'm trying to create a simple chart.</p>
  
  <pre><code>set datafile separator ","
  set xdata time   
  set timefmt "%d/%m/%Y %H:%M:%S" 
  set format x "%H:%M" 
  set autoscale y
  plot ["13:00":"14:00"] './data.csv' using 1:2 with lines
  </code></pre>
  
  <p>data.csv:</p>
  
  <pre><code>26/10/2010 13:30:01,1
  
  26/10/2010 13:30:12,2
  
  26/10/2010 13:30:23,3
  
  26/10/2010 13:30:34,4
  </code></pre>
  
  <p>gives me the error:</p>
  
  <pre><code>line 6: all points y value undefined!
  </code></pre>
  
  <p>I've tried all manners of timefmt settings!</p>
  
  <p>Many thanks</p>