title: How can I convert a week (200851) into a date (2008-12-27)?
body: <p>How could I convert a year-week (for example, 0852 or 200852) into a date (for example, 2008-12-31 or specifically a week-ending day, that is, Saturday 2008-12-27 or a week-beginning day, that is, 2008-12-21)?</p>
  <p>Any day of the week-ending will do, Friday, Saturday, Sunday or Monday.</p>