function y2k(number) { return (number < 1000) ? number + 1900 : number; }

function getWeek(year,month,day) {
    var when = new Date(year,month,day);
    var newYear = new Date(year,0,1);
    var modDay = newYear.getDay();
    if (modDay == 0) modDay=6; else modDay--;

    var daynum = ((Date.UTC(y2k(year),when.getMonth(),when.getDate(),0,0,0) -
                 Date.UTC(y2k(year),0,1,0,0,0)) /1000/60/60/24) + 1;

    if (modDay < 4 ) {
        var weeknum = Math.floor((daynum+modDay-1)/7)+1;
    }
    else {
        var weeknum = Math.floor((daynum+modDay-1)/7);
        if (weeknum == 0) {
            year--;
            var prevNewYear = new Date(year,0,1);
            var prevmodDay = prevNewYear.getDay();
            if (prevmodDay == 0) prevmodDay = 6; else prevmodDay--;
            if (prevmodDay < 4) weeknum = 53; else weeknum = 52;
        }
    }

    return + weeknum;
}

var now = new Date();
document.write('<a href="http://ugenr.dk/" target="_blank">');
document.write('Uge ' +
getWeek(y2k(now.getYear()),now.getMonth(),now.getDate()));
document.write('</a>');