JSFiddle - React, Tailwind, and code Playground

HTML

<div id="showTime"></div>
<div id='strtime'>

</div>

JavaScript

//This time variable sets the date to the action
//Use 24-hour time format
time = "21:12:30";

showDiff();


function strtotime(time){
    //Format of time: 21:56:00 hh:mm:ss    
    var time = time.split(":");
    var current = new Date();
    var todayMorning = current.getTime()/1000 - current.getHours()*60*60 - current.getMinutes()*60 - current.getSeconds();
    
    var strtotime = todayMorning + time[0]*60*60 + time[1]*60 + time[2];
   
    var strtotime = strtotime * 1000;
    var strtotime = new Date(strtotime);
    return strtotime;
    
}


function showDiff(){
    var current = new Date(); 
    var date = strtotime(time);
    document.getElementById("strtime").innerHTML = date;
    //Customise date2 for your required future time
    
    var diff = (date - current)/1000;
    var diff = Math.abs(Math.floor(diff));
    
    var days = Math.floor(diff/(24*60*60));
    var leftSec = diff - days * 24*60*60;
    
    var hrs = Math.floor(leftSec/(60*60));
    var leftSec = leftSec - hrs * 60*60;
      
    var min = Math.floor(leftSec/(60));
    var leftSec = leftSec - min * 60;
    
    
 
    
    document.getElementById("showTime").innerHTML = "You have " + days + " days " + hrs + " hours " + min + " minutes and " + leftSec + " seconds before death.";
    
setTimeout(showDiff,1000);
}