Q99 How can you display how many years, months & days are left until 31/12/1999?

<script language="JavaScript"><!--
function y2k(number) { return (number < 1000) ? number + 1900 : number; }

function timeTillDate(whenDay,whenMonth,whenYear) {
    var now = new Date();
    var thisDay = now.getDate(), thisMonth = now.getMonth() + 1, thisYear = y2k(now.getYear());
    var yearsDifference = whenYear - thisYear, monthsDifference = 0, daysDifference = 0, string = '';

    if (whenMonth >= thisMonth) monthsDifference = whenMonth - thisMonth;
    else { yearsDifference--; monthsDifference = whenMonth + 12 - thisMonth; }

    if (whenDay >= thisDay)daysDifference = whenDay - thisDay;
    else {
        if (monthsDifference > 0) monthsDifference--;
        else { yearsDifference--; monthsDifference+=11; }
        daysDifference = whenDay + 31 - thisDay;
    }

    if (yearsDifference < 0) return '';

    if ((yearsDifference == 0) && (monthsDifference == 0) && (daysDifference == 0))
        return '';

    if (yearsDifference > 0) {
        string = yearsDifference + ' year';
        if (yearsDifference > 1) string += 's';
        string += ' ';
    }

    if (monthsDifference > 0) {
        string += monthsDifference + ' month';
        if (monthsDifference > 1) string += 's';
        string += ' ';
    }

    if (daysDifference > 0) {
        string += daysDifference + ' day';
        if (daysDifference > 1) string += 's';
        string += ' ';
    }

    var difference = Date.UTC(y2k(now.getYear()),now.getMonth(),now.getDate(),now.getHours(),now.getMinutes(),now.getSeconds()) -
                     Date.UTC(y2k(now.getYear()),now.getMonth(),now.getDate(),0,0,0);

    difference = 1000*60*60*24 - difference;

    var hoursDifference = Math.floor(difference/1000/60/60);
    difference = difference - hoursDifference*1000*60*60
    var minutesDifference = Math.floor(difference/1000/60);
    difference = difference - minutesDifference*1000*60
    var secondsDifference = Math.floor(difference/1000);

    if (hoursDifference > 0) {
        string += hoursDifference + ' hour';
        if (hoursDifference > 1) string +='s';
        string += ' ';
    }

    if (minutesDifference > 0) {
        string += minutesDifference + ' minute';
        if (minutesDifference > 1) string +='s';
        string += ' ';
    }

    if (secondsDifference > 0) {
        string += secondsDifference + ' second';
        if (secondsDifference > 1) string +='s';
        string += ' ';
    }

    return string;
}

document.write(timeTillDate(31,12,1999));
//--></script>