title: Mutable Date class fix
body: <p>I am just wondering what would be the correct method of making the code below immutable. </p>
  
  <pre><code>Date d = new Date();
  Scheduler.scheduleTask(task1, d);
  d.setTime(d.getTime() + ONE_DAY);
  Scheduler.scheduleTask(task2, d);
  </code></pre>