title: Remove timestamp from matplotlib.num2date date, and use date stamp in axis xlabel
body: <p>I have an array of date values (T_date), imported from a CSV and converted to numbers using </p>
  
  <pre><code>T_date, T_price = np.loadtxt('TESC.csv', unpack = True, delimiter = ',',
                   skiprows=1, usecols=(0,4),
                   converters = {0: mdates.strpdate2num('%Y-%m-%d')}) 
  </code></pre>
  
  <p>I then create a new array starting from 0, with 0 being the earliest date using</p>
  
  <pre><code>T_date0=T_date-np.amin(T_date)
  </code></pre>
  
  <p>I wish to label the x axis of a pyplot plot as </p>
  
  <pre><code>plt.xlabel("Date, 0 = ", firstdate)
  </code></pre>
  
  <p>where firstdate=</p>
  
  <pre><code>firstdate = mdates.num2date(np.amin(T_date)).
  </code></pre>
  
  <p>This creates a datetime value in the form Y-m-d time, but as my data has no time values I wish to remove it.</p>
  
  <p>When I run this, I get the error </p>
  
  <pre><code>"AttributeError: 'datetime.datetime' object has no attribute 'iteritems'"
  </code></pre>
  
  <p>Any help much appreciated.</p>