function getSeconds() {
var now = new Date();
var time = now.getTime();  // time now in milliseconds
var midnight = new Date(now.getFullYear(),now.getMonth(),now.getDate(),0,0,0); // midnight 0000 hrs
// midnight - change time hh,mm,ss to whatever time required, e.g. 9,15,0 (0915)
var ft = midnight.getTime() + 86400000;  // add one day 12 hours
var diff = ft - time;  
diff = parseInt(diff/1000);
if (diff > 129600) {diff = diff - 129600}
startTimer (diff);
}


var timeInSecs;
var ticker;

function startTimer(secs){
timeInSecs = parseInt(secs);
ticker = setInterval("tick()",1000); 
tick(); // to start counter display right away
}

function tick() {
var secs = timeInSecs;
if (secs>0) {
timeInSecs--;
}
else {
clearInterval(ticker); // stop counting at zero
//getSeconds();  // and start again if required
}

var hours= Math.floor(secs/3600);
secs %= 3600;
var mins = Math.floor(secs/60);
secs %= 60;
var result = ((hours < 10 ) ? "0" : "" ) + hours + ":" + ( (mins < 10) ? "0" : "" ) + mins
                  + ":" + ( (secs < 10) ? "0" : "" ) + secs;
document.getElementById("countdown").innerHTML =  result;
}