Adding Functionality To Countdown Function

I've got the following JS function that does a basic countdown to a specific date. I have a series of dates, and rather than change the date manually each time the previous one has passed, I'd like to automate it a bit and have it just read the date from an array, and use that date for the countdown. The check would be if the countdown'd date has already passed. Here's what I currently have:

<script language="javascript">
// date/countdown

function showDate () {
var now = new Date();
var date = now.getDate();
var month = now.getMonth() + 1;
var year = now.getYear();

currentDate = now.getMonth() + 1;
window.status = month + "/" + date + "/" + year + " thisdomain.com ";

var roundCDiv = document.getElementById('roundC');
var showDate = month + "/" + date + "/" + year;
//roundCDiv.innerHTML = showDate;

// countdown
var nextDateB = new Date("October 30, 2005");
var diffB = nextDateB.getTime() - now.getTime();
var daysLeftB = Math.ceil(diffB / (1000 * 60 * 60 * 24));
var roundBDiv = document.getElementById('countdown');
//roundBDiv.innerHTML = daysLeftB + " days until ...;
roundBDiv.innerHTML = daysLeftB;
roundBDiv.innerHTML = daysLeftB + " ";
}

</script>