Countdown timer with php variables

Question

I have this code that countdown 1 minute:

<span id="hour">00</span>:<span id="min">00</span>:<span id="sec">00</span>

<script type="text/javascript" src="https://ajax.googleapis.com/ajax/libs/jquery/1.5.1/jquery.min.js"></script>
<script type="text/javascript">
var deadline = new Date("<?php echo date('M d, Y H:i:s', $regaptimer); ?>").getTime(); 
var now = new Date("<?php echo date('M d, Y H:i:s', $now_time); ?>").getTime(); 
var t;
var interval=36000*2;
$(document).ready(function(){

    startCounter();
});
function startCounter()
{
    t=setInterval(function(){decrement();},1000);
}
function decrement()
{
    if(interval>0)
    {
        interval-=1000;
        formatDate();
    //  console.log("hello");
    }
    else
    {
        clearInterval(t);
    }
}
function formatDate()
{
    var remain=interval;
    var hours=parseInt(remain/3600000);
    if(hours>0)
        remain=remain-(hours*3600000);

    var minutes=parseInt(remain/60000);

    if(minutes>0)
        remain=remain-(minutes*60000);


    var seconds=parseInt(remain/1000);

//  console.log(hours,minutes,seconds);
    if(hours>9)
    $("#hour").text(hours.toString());
    else
    $("#hour").text('0'+hours.toString());
    if(minutes>9)
    $("#min").text(minutes.toString());
    else
    $("#min").text('0'+minutes.toString());
    if(seconds>9)
    $("#sec").text(seconds.toString());
    else
    $("#sec").text('0'+seconds.toString());
}</script>```

And I want to set these variables

var deadline = new Date("<?php echo date('M d, Y H:i:s', $regaptimer); ?>").getTime();
var now = new Date("<?php echo date('M d, Y H:i:s', $now_time); ?>").getTime();
var t = deadline - now;

to countdown specific time between the ending point and the starting one. I cannot figure out how to do it. Any help would be great. Many thank you in advance

Best Regards Chris

EDIT: I found this code that seems to do it but doesn't include days and hours. i need serverside 100%. I found this code seems to do the trick but missing hours and days...

<span id="countdown" class="timer"></span>
<script>
var deadline = new Date("<?php echo date('M d, Y H:i:s', $regaptimer); ?>").getTime(); 
var now = new Date("<?php echo date('M d, Y H:i:s', $now_time); ?>").getTime(); 
var seconds = deadline - now; 
function secondPassed() {
    var minutes = Math.round((seconds - 30)/60);
    var remainingSeconds = seconds % 60;
    if (remainingSeconds < 10) {
        remainingSeconds = "0" + remainingSeconds;  
    }
    document.getElementById('countdown').innerHTML = minutes + ":" + remainingSeconds;
    if (seconds == 0) {
        clearInterval(countdownTimer);
        document.getElementById('countdown').innerHTML = "Buzz Buzz";
    } else {
        seconds--;
    }
}

var countdownTimer = setInterval('secondPassed()', 1000);
</script>

Anyone willing to help how to include them?