title: datetime format change when save to csv file python
body: <p>I have a dataframe like this:</p>
  
  <pre><code>In [67]:
  call_df.head()
  Out[67]:
  timestamp   types
  1   2014-06-30 07:00:55 Call_O
  2   2014-06-30 07:00:05 Call_O
  3   2014-06-30 06:54:55 Call_O
  501 2014-06-30 11:24:01 Call_O
  </code></pre>
  
  <p>When I saved that dataframe to csv file, the format of datetime is change as well as I lose the seconds. I just put this code to save into csv file:</p>
  
  <pre><code>call_df.to_csv('D:/Call.csv')
  </code></pre>
  
  <p>The csv file output is like this:</p>
  
  <p><img src="https://i.stack.imgur.com/Ec0Ku.png" alt="enter image description here"></p>
  
  <p>In here I want to ask, how to save the same datetime format from dataframe into csv file</p>