title: dialogflow sys.date-time parameter format question
body: <p>I'm making an app on Dialogflow and need to extract <code>date-time</code> info from user. So I specified a required parameter called "date-time" with @sys.date-time entity in my intent. However, when I tried to extract this parameter in my fulfillment code, I found that this parameter structure is not the same every time when I extract it. For example, when I type <code>12:30am</code> into the chatbot, the returned API json response contained this:</p>
  
  <pre><code>"parameters": {
        "date-time": "2019-11-27T00:30:00-08:00",
        "log": "5"
      },
  </code></pre>
  
  <p>So I can directly read <code>date-time</code> parameter value by <code>parameters['date-time']</code></p>
  
  <p>However, if I type "yesterday at 2pm" into chatbot, the returned parameter structure is this:</p>
  
  <pre><code>"parameters": {
        "date-time": {
          "date_time": "2019-11-25T14:00:00-08:00"
        },
        "log": "log"
      },
  
  </code></pre>
  
  <p>See that the "date-time" parameter is wrapped inside an extra "date-time" object. This is really annoying because now i need to consider these two cases in my fulfillment code. Does anyone know why this happened? And is this a bug on my side? Thanks!</p>