Per the ISO standard for date and time (8601), the method for numbering weeks is described here... http://en.wikipedia.org/wiki/ISO_week_date ...Since Jan 1, 2009 was a Thursday that makes that week, which goes Mon-Sun, Week 1. If Jan 1 were on a Fri, Sat, or Sun it would be in
Week 52 (or 53) of the previous year. Today, Sep 27, is the last day of Week 39.