title: get rows with empty dates pandas python
body: <p>it looks like this:</p>
  
  <pre><code>      Dates  N-D  unit
  0  1/1/2016  Q1   UD
  1            Q2   UD
  2            Q3   UD
  3  2/1/2016  Q4   UD
  4  5/1/2016  Q5   UD
  5            Q6   UD
  </code></pre>
  
  <p>I want to filter out the empty Dates rows and save it in a dataframe blankDate:</p>
  
  <pre><code>      Dates  N-D  unit
  1            Q2   UD
  2            Q3   UD
  5            Q6   UD
  
  
   blankDate=df1[df1['Dates']== '']  #this didn't work 
   df1['Discharge Date'] = pd.to_datetime(df1['Discharge Date']) #then I converted the column to date format but still doesn't work
  </code></pre>
  
  <p>if the column is a string this piece of code works, it also works on numbers I think</p>
  
  <pre><code>blankDate=df1[df1['stringcolumn']== '']
  </code></pre>
  
  <p>but how do I compare to empty date rows? </p>