title: Make new subsets for each month
body: <p>I try to make subsets of each month or quarter from my data frame. I already tried some StackOverflow suggestions with the DateTime package but without success. My data frame is a Pandas data frame where the date column consists of a TimeStamp object. If someone has a suggestion that could work that would be lovely.</p>
  
  <p>One of the best options from StackOverflow I already tried is:</p>
  
  <pre><code>date_format = "%Y-%m-%d %H:%M:%S"
  df['datetime'] = [datetime.strptime(dt, date_format) for dt in df['date']]
  df['quarter'] = [dt.quarter for dt in df['datetime']]
  dfQ1 = df[df.quarter == 1]
  # for each quarter the same
  </code></pre>
  
  <p>I made timestamps of my data by the use of the following code:</p>
  
  <pre><code>time_stamps = []
  for i in data['event_timestamp']:
  time_stamps.append(datetime.datetime.strptime(i, '%Y-%m-%d %H:%M:%S'))
  </code></pre>
  
  <p>You can find a picture of the head of the dataframe in the following link:
  <a href="https://i.stack.imgur.com/pFmD3.png" rel="nofollow noreferrer">head of the data frame</a></p>