title: Easily convert string column to pl.datetime in Polars
body: <p>Consider a Polars data frame with a column of <code>str</code> type that indicates the date in the format <code>'27 July 2020'</code>. I would like to convert this column to the <code>polars.datetime</code> type, which is distinct from the Python standard <code>datetime</code>. The following code, using the standard <code>datetime</code> format, works but Polars does not recognise the values in the column as dates.</p>
  <pre><code>import polars as pl
  from datetime import datetime
  
  df = pd.read_csv('&lt;some CSV file containing a column called 'event_date'&gt;')
  df = df.with_columns([   
          pl.col('event_date').apply(lambda x: x.replace(&quot; &quot;,&quot;-&quot;))\
                              .apply(lambda x: datetime.strptime(x, '%d-%B-%Y'))
  ])
  
  </code></pre>
  <p>Suppose we try to process <code>df</code> further to create a new column indicating the quarter of the year an event took place.</p>
  <pre><code>df = df.with_columns([
          pl.col('event_date').apply(lambda x: x.month)\
                              .apply(lambda x: 1 if x in range(1,4) else 2 if x in range(4,7) else 3 if x in range(7,10) else 4)\
                              .alias('quarter')
  ])
  </code></pre>
  <p>The code returns the following error because it qualifies <code>event_type</code> as <code>dtype Object(&quot;object&quot;)</code> and not as <code>datetime</code> or <code>polars.datetime</code></p>
  <pre><code>thread '&lt;unnamed&gt;' panicked at 'dtype Object(&quot;object&quot;) not supported', src/series.rs:992:24
  --- PyO3 is resuming a panic after fetching a PanicException from Python. ---
  PanicException: Unwrapped panic from Python code
  </code></pre>