Countdown

HTML

<div id="timeremaining"></div>

JavaScript

var target_date = new Date('June 21 2016 20:00:00').getTime();

var localMinDiff = new Date().getTimezoneOffset() * 60000;  // get the difference between local time and GMT >> in mins >> mins to milliseconds conversion
target_date = target_date - localMinDiff;
var days, hours, minutes, seconds;
        var countdown = document.getElementById('timeremaining');
        var countdownTimer = setInterval(function () {
            var current_date = new Date().getTime();
            var seconds_left = (target_date - current_date) / 1000;
 
            days = parseInt(seconds_left / 86400);
            seconds_left = seconds_left % 86400;
                        
            hours = parseInt(seconds_left / 3600);
            seconds_left = seconds_left % 3600;
            minutes = parseInt(seconds_left / 60);
            seconds = parseInt(seconds_left % 60);
            
            if(days <= 0 && hours <= 0 && minutes <= 0 && seconds <= 0 )
            {
               countdown.innerHTML = '';
               clearInterval(countdownTimer);
            }
            else
            {       
                if(days>0)
	              {
	                 days= '<b>'+days+'days, '+'</b>';
	              }	
	              else
	              {
	                 days='';
	              }            
                countdown.innerHTML = 'Next class in: ' + days + checkTime(hours) + ':'+ checkTime(minutes) + ':' + checkTime(seconds);  	
            }
        }, 1000);

        function checkTime(i) {
            if (i < 10) {i = '0' + i};  
            return i;
        }