title: Datetime milliseconds to seconds in Pandas
body: <p>Have a datetime column in pandas dataframe with values like these:</p>
  
  <pre><code>time
  2018-04-11 22:18:30.122
  2018-04-11 23:00:21.399
  </code></pre>
  
  <p>I'm wondering how can I round these values, get rid of milliseconds and represent only date, hour, minutes and 00 as seconds like this:</p>
  
  <pre><code>time
  2018-04-11 22:18:00
  2018-04-11 23:00:00
  </code></pre>