title: How can I create a datetime column without 'date' part?
body: <p>I have a dataframe and there's a column named 'Time' in it like the below(HH:MM:SS:fffff).</p>
  
  <pre><code>&gt;&gt;&gt; df['Time']
  0        09:42:29:75284
  1        09:42:29:95584
  2        09:42:31:15036
  3        09:42:35:15138
  4        09:42:35:95491
  5        09:42:43:55414
  6        09:42:45:35866
  7        09:42:46:74638
  8        09:42:47:35582
  9        09:42:47:74774
  10       09:42:48:94582
  ...
  Name: Time, Length: 18924, dtype: object
  </code></pre>
  
  <p>I want to change its type as datetime, in order to make it easier to calculate. Is it possible to change its type, using pandas.to_datetime, as datetime without date?</p>