title: How to keep the same datatype after saving data to CSV file?
body: <p>I'm saving data to CSV files using pandas. I have one important column with dtype: datetime64[ns].Somehow the datatype is changed to object when I read the data back from CSV file. How can I write, read while keeping the same datatype? Is this related to the encoding type?</p>
  
  <pre><code>df = pd.io.sql.read_sql(sql, cnxn)
  df.to_csv(fileName)
  df.TimeSeries
  </code></pre>
  
  <blockquote>
    <p>Name: TimeSeries, Length: 10000, dtype: datetime64[ns]</p>
  </blockquote>
  
  <pre><code>DF = pd.read_csv(fileName, sep=',')
  DF.TimeSeries
  </code></pre>
  
  <blockquote>
    <p>Name: TimeSeries, Length: 10000, dtype: object</p>
  </blockquote>