title: TypeError: <class 'datetime.time'> is not convertible to datetime
body: <p>The problem is somewhat simple. My objective is to compute the days difference between two dates, say A and B.</p>
  <p>These are my attempts:</p>
  <pre><code>df['daydiff'] = df['A']-df['B']
  
  df['daydiff'] = ((df['A']) - (df['B'])).dt.days
  
  df['daydiff'] = (pd.to_datetime(df['A'])-pd.to_datetime(df['B'])).dt.days
  </code></pre>
  <p>These works for me before but for some reason, I'm keep getting this error this time:</p>
  <blockquote>
  <p>TypeError: class 'datetime.time' is not convertible to datetime</p>
  </blockquote>
  <p>When I export the df to excel, then the date works just fine. Any thoughts?</p>