title: convent and find The difference between date time flutter
body: <p>I need to help with my fluter code,
  I have an API its response me a date as a String</p>
  
  <pre><code> {"time": "12/04/2020 16:09:33"}
  </code></pre>
  
  <p>and I get the current time in my code from the phone using </p>
  
  <pre><code>var now = new DateTime.now();
  </code></pre>
  
  <p>how I can calculate the difference between two date-time???</p>