function calculate_time($start, $end) {
		$return = '';
		//echo "Start:$start, end:$end\n";
		if (!$end) {
			$return .= '<div id="timer">';
			$timer = true;
			$end = time();
		} else {
			$timer = false;
		}
		$min = 60;
		$hour = $min * 60;
		$_timer = $diff = $end - $start;
		$hours = floor($diff / $hour);
		$diff = ($diff - ($hours * $hour));
		$mins = floor($diff / $min);
		$diff = ($diff - ($mins * $min));
		
		if ($hours) {
			$return .= "$hours:";
		}
		if ($mins <= 9 && $return) {
			$return .= "0$mins:";
		} else {
			$return .= "$mins:";
		}
		if ($diff == 0) {
			$diff = '0';
		}
		if ($diff <= 9) {
			$diff = "0$diff";
		}
		if ($timer) {
			$diff .= "</div><script language='JavaScript' type='text/javascript'><!--
			
			timer = $_timer;
			
			//--></script>";
		}
		return $return.$diff;
	}