how to countdown to a date

This is working fine as a normal javascript.

<script>
var end = new Date('02/19/2012 10:1 AM');

    var _second = 1000;
    var _minute = _second * 60;
    var _hour = _minute * 60;
    var _day = _hour * 24;
    var timer;

    function showRemaining() {
        var now = new Date();
        var distance = end - now;
        if (distance < 0) {

            clearInterval(timer);
            document.getElementById('countdown').innerHTML = 'EXPIRED!';

            return;
        }
        var days = Math.floor(distance / _day);
        var hours = Math.floor((distance % _day) / _hour);
        var minutes = Math.floor((distance % _hour) / _minute);
        var seconds = Math.floor((distance % _minute) / _second);

        document.getElementById('countdown').innerHTML = days + 'days ';
        document.getElementById('countdown').innerHTML += hours + 'hrs ';
        document.getElementById('countdown').innerHTML += minutes + 'mins ';
        document.getElementById('countdown').innerHTML += seconds + 'secs';
    }

    timer = setInterval(showRemaining, 1000);
</script>
<div id="countdown"></div>

Your output is appearing as follows:-

1days 9hrs 3mins 22secs

UPDATE

Using Functions:

<script>

    CountDownTimer('02/19/2012 10:1 AM', 'countdown');
    CountDownTimer('02/20/2012 10:1 AM', 'newcountdown');

    function CountDownTimer(dt, id)
    {
        var end = new Date(dt);

        var _second = 1000;
        var _minute = _second * 60;
        var _hour = _minute * 60;
        var _day = _hour * 24;
        var timer;

        function showRemaining() {
            var now = new Date();
            var distance = end - now;
            if (distance < 0) {

                clearInterval(timer);
                document.getElementById(id).innerHTML = 'EXPIRED!';

                return;
            }
            var days = Math.floor(distance / _day);
            var hours = Math.floor((distance % _day) / _hour);
            var minutes = Math.floor((distance % _hour) / _minute);
            var seconds = Math.floor((distance % _minute) / _second);

            document.getElementById(id).innerHTML = days + 'days ';
            document.getElementById(id).innerHTML += hours + 'hrs ';
            document.getElementById(id).innerHTML += minutes + 'mins ';
            document.getElementById(id).innerHTML += seconds + 'secs';
        }

        timer = setInterval(showRemaining, 1000);
    }

</script>
<div id="countdown"></div>
<div id="newcountdown"></div>

Output will appear as follows:-

0days 23hrs 25mins 8secs

1days 23hrs 25mins 8secs

That's not jQuery, that's JavaScript. But anyways...

You almost got it. The only issue is var distance = end-now;. It should be:

var distance = end.getTime()-now.getTime();

Also, you shouldn't use += on innerHTML. Instead, use a variable (example: var output = "") and add to that, then assign to the innerHTML at the end.

Finally, double-check that the ID of the div matches the ID you have in getElementById.