title: Merging pandas dataframe
body: <p>I have two dfs, one called master:</p>
  
  <pre><code>     ARI     Flesch    Kincaid      time  VIX_close  FEDFUNDS  \
  15.219540  40.099442  14.969857  01/02/08  26.128000  4.220000   
  19.154130  38.308678  16.955482  01/02/08  26.128000  4.220000   
  17.859696  35.896056  15.457418  01/02/13  13.446333  0.158667
  
   Baseline_overall_index  News_Based_Policy_Uncert_Index  
               110.973189                      120.994318  
               110.973189                      120.994318  
               190.472390                      213.912415  
  </code></pre>
  
  <p>the second is called data:</p>
  
  <pre><code>     ARI     Flesch    Kincaid                 Speaker     Score  \
  19.285543  26.507396  17.649118             Minutes FRC -1.697248   
  15.010289  42.676816  13.966083  J. Alfred Broaddus Jr.  0.403775   
  15.009436  42.707457  13.961809                     NaN  0.312579
  
      time
  02/04/16
  08/16/16
  09/28/16
  </code></pre>
  
  <p>I would like to merge the dfs on 'time' which is a datetime object. Also, individual days are missing from data df, while all days are filled in master though both dfs may have duplicate entries per individual day.</p>
  
  <p>Running the code below I get the following output:</p>
  
  <p>Code:</p>
  
  <pre><code>remix = pd.merge(master, data)
  </code></pre>
  
  <p>Output:</p>
  
  <pre><code>Empty DataFrame
  Columns: [ARI, Flesch, Kincaid, time, VIX_close, FEDFUNDS, 
  Baseline_overall_index, News_Based_Policy_Uncert_Index, Speaker, 
  Score, Residual, Date]
  Index: []
  </code></pre>