title: Duration.ofDays generates UnsupportedTemporalTypeException
body: <p>I am trying to learn the new <a href="https://docs.oracle.com/javase/tutorial/datetime/iso/index.html" rel="noreferrer">Date &amp; Time API</a>. My code is working except for the last line:</p>
  
  <pre><code>LocalDate current=LocalDate.now();
  System.out.println(current);
  
  LocalDate personaldate=LocalDate.of(2011,Month.AUGUST, 15);
  System.out.println(personaldate);
  
  LocalDate afterten=current.plus(Period.ofDays(10));
  System.out.println(afterten);
  
  // error occurs here        
  System.out.println(afterten.plus(Duration.ofDays(3)));
  </code></pre>
  
  <p>When I try and add a Duration in days, it generates an error. Can anyone help me understand why? </p>
  
  <p><strong>Error:</strong>    </p>
  
  <pre><code>Exception in thread "main" java.time.temporal.UnsupportedTemporalTypeException: Unsupported unit: Seconds                                                                                             
          at java.time.LocalDate.plus(LocalDate.java:1241)                                                                                                                                              
          at java.time.LocalDate.plus(LocalDate.java:137)                                                                                                                                               
          at java.time.Duration.addTo(Duration.java:1070)                                                                                                                                               
          at java.time.LocalDate.plus(LocalDate.java:1143)                                                                                                                                              
          at TestClass.main(TestClass.java:15)    
  </code></pre>