title: how do i get the 1st day of week from current date
body: <p>I would like get the 1st date of week?<br>
  ie.</p>
  
  <pre><code> if 2011-01-01 then 2011-01-01  
      if 2011-01-06 then 2011-01-01  
      if 2011-01-20 then 2011-01-14  
      if 2011-01-21 then 2011-01-21 
  </code></pre>
  
  <p>Sorry for misleading and making question confusion.</p>
  
  <p>I just want to get the date of the 1st day of the week, ie. either 1 or 7 or 14 or 21 or 28 </p>