Auto restart this countdown?

Here is the script. It is set to countdown to 4:20 but once 4:20 came around it just went blank and wont restart. Any hep?

// ****  Time Zone Count Down Javascript  **** //
/*
Visit http://rainbow.arch.scriptmania.com/scripts/
 for this script and many more
*/

////////// CONFIGURE THE COUNTDOWN SCRIPT HERE //////////////////

var month = '0';     //  '*' for next month, '0' for this month or 1 through 12 for the month 
var day = '+0';       //  Offset for day of month day or + day  
var hour = 16;        //  0 through 23 for the hours of the day
var min = 20; 
var tz = -5;         //  Offset for your timezone in hours from UTC
var lab = 'tzcd';    //  The id of the page entry where the timezone countdown is to show

function start() {displayTZCountDown(setTZCountDown(month,day,hour,tz),lab);}

    // **    The start function can be changed if required   **
window.onload = start;

////////// DO NOT EDIT PAST THIS LINE //////////////////

function setTZCountDown(month,day,hour,tz) 
{
var toDate = new Date();
if (month == '*')toDate.setMonth(toDate.getMonth() + 1);
else if (month > 0) 
{ 
if (month <= toDate.getMonth())toDate.setYear(toDate.getYear() + 1);
toDate.setMonth(month-1);
}
if (day.substr(0,1) == '+') 
{var day1 = parseInt(day.substr(1));
toDate.setDate(toDate.getDate()+day1);
} 
else{toDate.setDate(day);
}
toDate.setHours(hour);
toDate.setMinutes(20-(tz*60));
toDate.setSeconds(0);
var fromDate = new Date();
fromDate.setMinutes(fromDate.getMinutes() + fromDate.getTimezoneOffset());
var diffDate = new Date(0);
diffDate.setMilliseconds(toDate - fromDate);
return Math.floor(diffDate.valueOf()/1000);
}
function displayTZCountDown(countdown,tzcd) 
{
if (countdown < 0) document.getElementById(tzcd).innerHTML = "Sorry, you are too late."; 
else {var secs = countdown % 60; 
if (secs < 10) secs = '0'+secs;
var countdown1 = (countdown - secs) / 60;
var mins = countdown1 % 60; 
if (mins < 10) mins = '0'+mins;
countdown1 = (countdown1 - mins) / 60;
var hours = countdown1 % 24;
var days = (countdown1 - hours) / 24;
document.getElementById(tzcd).innerHTML = +hours+ 'h : ' +mins+ 'm : '+secs+'s';
setTimeout('displayTZCountDown('+(countdown-1)+',\''+tzcd+'\');',999);
}
}

Code (markup):

 

Anyone have a idea?

 

yeah, but unfortunately, it says:

and the bit you want changed is there...
























try this:
find:
if (countdown < 0) document.getElementById(tzcd).innerHTML = "Sorry, you are too late.";
else {

replace with:

if (countdown < 0) {
hour = 16; // reset values
min = 20;
var countdown = setTZCountDown(month,day,hour,tz);
}
// remove else and matching { }
// {
...

// }