title: Identify the Friday (or other specific weekday) before sysdate
body: <p>I need to return the date of the last Friday before the <code>SYSDATE</code>.</p>
  
  <p>To be clear:</p>
  
  <ul>
  <li>If I ran the script today (Thursday 29th September), I would want last Friday's date to be returned (Friday 22nd September).</li>
  <li>If I run the script two days from now (Saturday 1st October), I would want tomorrows date to be returned (Friday 30th September).</li>
  </ul>