title: Convert date from yyyymmddHHMMSS format
body: <p>I would like to read two columns (columns 0, 4) of the following ascii file and plot them. One contains the date in yyymmddHHMMSS format which I would like to covert to a date number.</p>
  
  <pre><code># Date          RMS.I   RMS.Q   Cal.I   Cal.Q      
  20121220220000 1.45485 1.42051 1.26393 1.29448
  20121220230000 1.43377 1.39987 1.26803 1.29874
  20121221000000 1.44888 1.41472 1.24759 1.27771
  </code></pre>
  
  <p>I have been using numpy.loadtxt but it reads all columns as float.</p>
  
  <pre><code>mydate, myvar = np.loadtxt('infile.txt', comments="#", skiprows=1, usecols=(0,4), unpack=True)
  </code></pre>