JSFiddle - React, Tailwind, and code Playground

HTML

<div id="counter">Loading...</div>

JavaScript

function myCounter(o, timeArray){
         var counter = document.getElementById(o);
         if(!counter) {
             return;
         }

         // helper functions
         function mksec(day, h, m, s){ return day*24*60*60+h*60*60+m*60+s; }
         function toTimeString(sec, showZero){
             var d=Math.floor(sec/(60*60*24))
             var h=Math.floor(sec/(60*60)%24);
             var m=Math.floor((sec/60) % 60);
             var s=sec % 60;
             var ret=d+' days '+h+' hours '+m+' minutes '+s+' seconds';
             if(showZero){
                return ret;
             }else if(d==0 && h==0 && m==0){
                return s+' seconds';
             }else if(d==0){
                return h+' hours '+m+' minutes '+s+' seconds';
             }else if(d==0 && h==0){
                return m+' minutes '+s+' seconds';
             }else {
                return ret;
             }
         }
         //
         var secArray = [];
         var dayNow = new Date().getDay();
         for(var i=0;i<timeArray.length;i++){
            var day=timeArray[i][0];
            if(day==-1){
                day=dayNow;
            }
             secArray.push({
                day: timeArray[i][0],
                sec: mksec(day, timeArray[i][1], timeArray[i][2], timeArray[i][3]),
                msg: timeArray[i][4] || false,
                showZero: timeArray[i][5] || false
             });
         }
         secArray.sort(function(a,b){ return a.sec-b.sec;});

         // timer code - will be called around each second (~1000 ms)
         function updateCounter(){
             // get current UTC time in seconds
             var d=new Date();
             var secNow = mksec(d.getDay(), d.getUTCHours(), d.getUTCMinutes(), d.getUTCSeconds());
             // find next event
             var nextIndex=0;
             for(var i=0;i<secArray.length; i++){
                 var diff = secArray[i].sec-secNow;
                 if(diff>0){
                    ...