title: Find the key for the latest date value represented as string
body: <p>How do I find the key for the latest date value of a dictionary where the dates are represented as strings?  </p>
  
  <p>I tried using <code>max(date, key=date.get)</code> as in <a href="https://stackoverflow.com/a/280156/7851470"><em>Getting key with maximum value in dictionary?</em></a>, but it returns wrong results: </p>
  
  <pre><code>date = {"sale_date": "2018-02-17 20:11:37.017298",
          "buy_date": "2018-02-2 20:11:37.017298"}
  
  latest = max(date, key=date.get) 
  </code></pre>
  
  <p>This returns <code>"buy_date"</code> but clearly the result should be <code>"sale_date"</code>.</p>