title: numpy datetime64 from day, month, year series
body: <p>I have dates are three numpy arrays containing each all the days, months or years separately.</p>
  
  <p>From these date-components I would like to construct a numpy.datetime64 array:</p>
  
  <pre><code>date = np.datetime64(days, months, years)
  </code></pre>
  
  <p>Of course the above does not work. The numpy documentation is silent on how to parse dates from anything other than strings.</p>
  
  <p>I am sure somebody has already solved this riddle before...</p>