function getYearlyWeekNumber(myDate)
{
    var this_date = new Date(myDate.getFullYear(),myDate.getMonth(),myDate.getDate(),0,0,0);
    var y_first_day = new Date(myDate.getFullYear(),0,1,0,0,0);
    var y_first_sun = new Date(myDate.getFullYear(),0,1+y_first_day.getDay(),0,0,0);
    var y_last_sat_before = new Date(myDate.getFullYear(),myDate.getMonth(),myDate.getDate()-myDate.getDay()+1,0,0,0);
    var y_sundaycount = dateDiff('ww', y_first_sun, y_last_sat_before);
    return y_sundaycount + ((y_first_day.getDay()<3) ? 1 : 2);
}