title: Pandas: slow date conversion
body: <p>I'm reading a huge <code>CSV</code> with a date field in the format <code>YYYYMMDD</code> and I'm using the following lambda to convert it when reading:</p>
  
  <pre><code>import pandas as pd
  
  df = pd.read_csv(filen,
                   index_col=None,
                   header=None,
                   parse_dates=[0],
                   date_parser=lambda t:pd.to_datetime(str(t),
                                              format='%Y%m%d', coerce=True))
  </code></pre>
  
  <p>This function is very slow though. </p>
  
  <p>Any suggestion to improve it?</p>