title: Reset time part of a pandas timestamp
body: <p>How can I reset the time part of a pandas timestamp?</p>
  
  <p>I want to reset time part in value of pandas.Timestamp.<br>
  I guess I can do it using the following procedure.</p>
  
  <ul>
  <li>step 1) Timestamp to datetime type</li>
  <li>step 2) datetime to seconds</li>
  <li>step 3) truncate time part in seconds</li>
  <li>step 4) bring back seconds to Timestamp</li>
  </ul>
  
  <p>Even if my guess is correct, it takes too long to do.
  Is there a straightforward way to achieve this goal?</p>
  
  <blockquote>
    <p>In [371]: ts = pd.Timestamp('2014/11/12 13:35')</p>
    
    <p>In [372]: ts</p>
    
    <p>Out[372]: Timestamp('2014-11-12 13:35:00')</p>
    
    <p>In [373]: ts.hour = 0 # &lt;-- this is what I am trying to do.</p>
  </blockquote>