flex 计算指定日期是本年度第几周

 /**
   * 计算指定日期是本年度第几周

   *传日年月日，返回number
   */
  private function weekOfYear(yyyy:Number,mm:Number,dd:Number):Number{ 
        var myDate:Date =new Date(yyyy, mm - 1, dd); 
        var startDate:Date = new Date(yyyy,0,1); 
        var diff:Number = myDate.valueOf() - startDate.valueOf(); 
        var d:Number = Math.round(diff/86400000); 
      return Math.ceil((d + ((startDate.getDay() + 1) - 1)) / 7); 
  }