function countdown(targetDate, uniqueId) {

    //get timeleft
    target = targetDate;

    var now = new Date();
    var millisecondsLeft = target.getTime() - now.getTime();

    var secondsLeft, minutesLeft, hoursLeft, daysLeft;
    var labelSeconds, labelMinutes, labelHours, labelDays;

    if (millisecondsLeft > 0) {
        //create formatted strings
        secondsLeft = Math.floor(millisecondsLeft / 1000);
        minutesLeft = Math.floor(secondsLeft / 60);
        hoursLeft = Math.floor(minutesLeft / 60);
        daysLeft = Math.floor(hoursLeft / 24);

        labelSeconds = secondsLeft % 60 + '';
        labelMinutes = minutesLeft % 60 + '';
        labelHours = hoursLeft % 24 + '';
        labelDays = daysLeft + '';

        // add extra zero: 0-9 becomes 00-09
        if (labelSeconds.length < 2)
            labelSeconds = "0" + labelSeconds;
        if (labelMinutes.length < 2)
            labelMinutes = "0" + labelMinutes;
        if (labelHours.length < 2)
            labelHours = "0" + labelHours;
        if (labelDays.length < 2)
            labelDays = "0" + labelDays;
    } else {
        //countdown complete
        labelSeconds = "00";
        labelMinutes = "00";
        labelHours = "00";
        labelDays = "00";
    }

    //set text labels
    document.getElementById(uniqueId+"_seconds").innerHTML = labelSeconds;
    document.getElementById(uniqueId+"_minutes").innerHTML = labelMinutes;
    document.getElementById(uniqueId+"_hours").innerHTML = labelHours;
    document.getElementById(uniqueId+"_days").innerHTML = labelDays;
}