title: Can only use .dt accessor with datetimelike values
body: <p>When i trying to convert the string to datetime, I am facing some issues.</p>
  
  <pre><code>testdata['pe']
  Out[69]: 
  0     2019-09-26
  1     2019-10-31
  2     2019-08-28
  3     2019-06-20
  4     2019-09-30
  5     2019-07-22
  6     2019-07-31
  7     2019-08-30
  8     2019-07-29
  9     2019-06-28
  10    2019-11-20
  Name: prd_exp_dt, dtype: object
  </code></pre>
  
  <p>When i did, <code>testdata.pe=testdata.pe.dt.strftime('%Y%M')</code>, i get this error:</p>
  
  <pre><code>Can only use .dt accessor with datetimelike values
  </code></pre>
  
  <p>Tried to do errors:"corerce", like this: </p>
  
  <pre><code>pandas.to_datetime(testdata['prd_exp_dt'],errors = 'coerce',format = '%Y%M')
  Out[68]: 
  0    NaT
  1    NaT
  2    NaT
  3    NaT
  4    NaT
  5    NaT
  6    NaT
  7    NaT
  8    NaT
  9    NaT
  10   NaT
  Name: prd_exp_dt, dtype: datetime64[ns]
  </code></pre>
  
  <p>Need some guidance on this.</p>