title: How do I repeat a DatetimeIndex in pandas
body: <p>How do I create a repeating date range? For example, I would like the following to repeat three times<br></p>
  <pre><code>rng = pd.date_range('1/1/2011', periods=3, freq='W')
  </code></pre>
  <p>Expected output:<br>
  2011-01-02<br>
  2011-01-09<br>
  2011-01-16<br>
  2011-01-02<br>
  2011-01-09<br>
  2011-01-16<br>
  2011-01-02<br>
  2011-01-09<br>
  2011-01-16<br></p>
  <p>I have tried:<br></p>
  <p>rng = pd.concat([rng] * 3, axis=1) #which does not work with dates<br>
  rng = np.repeat(rng,3) #this repeats each date three times instead of the list three times?</p>