JSFiddle - React, Tailwind, and code Playground

HTML

<time dataTime="1414512000000"></time>

JavaScript

function dateTime(){
	var elementos = document.getElementsByTagName("time"),
		total = elementos.length,
		now = new Date(),
		local_seconds_now = now.getTime();
	for (var i = 0; i < total; i++){
		var utc_seconds = elementos[i].getAttribute("dateTime"),
		utc_seconds_now = Date.UTC(now.getFullYear(),now.getMonth(), now.getDate(), now.getHours(), now.getMinutes(), now.getSeconds(), now.getMilliseconds());
	 	from_utc_to_local = utc_seconds + (utc_seconds_now - local_seconds_now),
		seconds_ago_local = local_seconds_now - from_utc_to_local; 
		elementos[i].innerHTML = seconds_ago_local;
	}
}
dateTime();
setInterval(function(){ dateTime() }, 60000);