title: serialise Date object to JSON using Gson in a custom way (annotation)
body: <p>I've got a following structure of classes</p>
  
  <pre><code>class A {
    B b;
  }
  
  class B {
      @CustomDateFormat(
          format = "yyyy-MM-dd"
      )
      protected Date creationDate;
  }
  </code></pre>
  
  <p>I'd like to serialise an instance of class A to JSON in the way that the output JSON has creationDate field formatted using the value in the annotation @CustomDateFormat. Is it possible? Ideally using Gson. That will be executed on Android so no Java 8 features ATM.</p>
  
  <p>thanks in advance for any ideas</p>