title: date_parser format not being recognized for one of two similar files
body: <p>I am trying to read a large .csv file that has date and time as the first column</p>
  
  <p>I have tried stating the format with which the datetime column needs to be read</p>
  
  <pre><code>def csv_to_df(file_path):
      dateparse = lambda x: pd.to_datetime(x, format = "%Y-%m-%d %H:%M:%S")
      df = pd.read_csv(file_path, skipinitialspace = True, parse_dates = ['Time'], date_parser=dateparse, index_col="Time")
      return df  
  filename = 'somefilename'
  df_sr = csv_to_df('somefilepath' + filename + '.csv')
  </code></pre>
  
  <p>For some files, it works and I can move on to the step to plot graphs. For others, I get the following error message:</p>
  
  <p>ValueError: time data '7/27/19 1:30' does not match format '%m-%d-%y %H:%M' (match)</p>