title: How is the Timer class in Java sensitive to the system clock?
body: <p>This <a href="https://stackoverflow.com/a/409993/1527084">highly voted answer on SO</a> regarding the differences between a <code>Timer</code> and a <code>ScheduledThreadPoolExecutor</code> mentions the following while enumerating the differences:</p>
  
  <blockquote>
    <p>Timer can be sensitive to changes in the system clock,
    ScheduledThreadPoolExecutor isn't.</p>
  </blockquote>
  
  <p>The above is mentioned verbatim inside the great book Java Concurrency in Practice.</p>
  
  <p>I understand the points mentioned in that answer except the above mentioned one. What does it mean to say that <code>Timers</code> can be sensitive to system clock whereas <code>ScheduledThreadPoolExecutors</code> are not?</p>