title: Excel WEEKNUM function Return_type
body: <p>The WEEKNUM function syntax has the following arguments:</p>
  
  <pre><code>WEEKNUM(serial_number,[return_type])
  </code></pre>
  
  <p>Return_type     Optional. A number that determines on which day the week begins.</p>
  
  <p>Please show an examples what's the difference between Return_type 2,11 and 21 ? Beacause i cant reproduce diff</p>