var timerID = null;
var timerRunning = false;

function stopclock (){
	if(timerRunning){
		clearTimeout(timerID);
		timerRunning = false;
	}
}

function showtime () {
	var now = new Date();
	var hours = now.getHours();
	var minutes = now.getMinutes();
	var seconds = now.getSeconds()
	if(minutes < 10) minutes="0" + minutes;
	if(seconds < 10) seconds="0" + seconds;
	var timeValue = hours + ":" + minutes + ":" + seconds;

	document.getElementById("clock").innerHTML = timeValue; 

	timerID = setTimeout("showtime()",1000);
	timerRunning = true;
}

function startclock() {
	stopclock();
	showtime();
}