title: showing milliseconds in matplotlib
body: <p>I'm using matplotlib to plot data as a function of time in hh:mm:ss.ms format where ms is milliseconds. However, I don't see the milliseconds in the plot. Is it possible to add them as well?  </p>
  
  <pre><code>dates = matplotlib.dates.datestr2num(x_values) # convert string dates to numbers
  plt.plot_date(dates, y_values)  # doesn't show milliseconds
  </code></pre>