var changeStart = todayInSeconds(changeHour, changeMinute, changeSecond);
var changeEnd = changeStart+changeDurationSeconds;
var interval = setInterval("tickTock()", 500); // Fires twice a second

function todayInSeconds(h, m, s) {
	if (h>11) h-=12; // Convert to 12 hr clock
	return (h*60*60)+(m*60)+s;
}

function tickTock() {
	var currentTime = new Date();
	var currentHour = currentTime.getHours();
	var currentMinute = currentTime.getMinutes();
	var currentSecond = currentTime.getSeconds();
	var currentTimeInSeconds = todayInSeconds(currentHour, currentMinute, currentSecond);

	if (changeStart <= currentTimeInSeconds && currentTimeInSeconds < changeEnd) {
		window.location = alternateURL;
	}
}