title: AttributeError: 'Timestamp' object has no attribute 'timestamp'
body: <p>I am struggling to get my code running. There seems to be a problem with the timestamp. Do you have any suggestions to how I could change my code? 
  I saw that this had been asked before, but did not manage to make it work.</p>
  
  <p>This is the error I get when running the code: <code>'Timestamp' object has no attribute 'timestamp'</code></p>
  
  <p>My code: </p>
  
  <pre><code>import quandl, math, datetime
  
  last_date = df.iloc[-1].name
  last_unix = last_date.timestamp()
  one_day = 86400 #Seconds in a day
  next_unix = last_unix + one_day
  
  
  for i in forecast_set: 
      next_date = datetime.datetime.fromtimestamp(next_unix)
      next_unix += one_day
      df.loc[next_date]=[np.nan for _ in range(len(df.columns)-1)]+[i]
      #Loop to replace all numbers on x axis with dates
  </code></pre>