title: Cron Expression - Starting at specific day/time and repeating till end of year
body: <p>I want to write a cron expression which does the following - </p>
  
  <p>Starting every last Sunday of September at 9:00 am and repeating every 3 weeks till end of the year.</p>
  
  <p>I have come up with </p>
  
  <pre><code>0 0 9 ? 9 6L
  </code></pre>
  
  <p>How can i make this repeat every two weeks till end of the year.</p>
  
  <p>Thanks in advance</p>