a simple count down core code

countdown.js

var deadline = "Thu, Feb 22 2017 23:59:59 GMT-0500";

// get the time remaining
function getTimeRemaining(endtime) {
  var t = Date.parse(endtime) - Date.parse(new Date());

  var seconds = (t / 1000) % 60;
  var minutes = Math.floor((t / 1000 / 60) % 60);
  var hours = Math.floor((t / (1000 * 60 * 60)) % 24);
  var days = Math.floor(t / (1000 * 60 * 60 * 24));
  return {
    'total': t,
    'days': days,
    'hours': hours,
    'minutes': minutes,
    'seconds': seconds
  };
}

// initialize clock
function initializeClock(id, endtime) {
  var clock = document.getElementById(id);
  var daysSpan = clock.querySelector('.days');
  var hoursSpan = clock.querySelector('.hours');
  var minutesSpan = clock.querySelector('.minutes');
  var secondsSpan = clock.querySelector('.seconds');

  function updateClock() {
    var t = getTimeRemaining(endtime);

    daysSpan.innerHTML = t.days;
    hoursSpan.innerHTML = ('0' + t.hours).slice(-2);
    minutesSpan.innerHTML = ('0' + t.minutes).slice(-2);
    secondsSpan.innerHTML = ('0' + t.seconds).slice(-2);

    if (t.total <= 0) {
      clearInterval(timeinterval);
      daysSpan.innerHTML = 0;
      hoursSpan.innerHTML = 0;
      minutesSpan.innerHTML = 0;
      secondsSpan.innerHTML = 0;
    }
  }

  updateClock();
  var timeinterval = setInterval(updateClock, 1000);
}

// var deadline = new Date(Date.parse(new Date()) + 97 * 24 * 60 * 60 * 1000);
initializeClock('clockdiv', deadline);

This code is not working in MAC safari....
The code i have used with my custom requirement
This Code works perfectly for mozilla and Crome...

$('#redirect_url').removeAttr('href');
        var vis = (function(){
            var stateKey, eventKey, keys = {
                hidden: "visibilitychange",
                webkitHidden: "webkitvisibilitychange",
                mozHidden: "mozvisibilitychange",
                msHidden: "msvisibilitychange"
            };
            for (stateKey in keys) {
                if (stateKey in document) {
                    eventKey = keys[stateKey];
                    break;
                }
            }
            return function(c) {
                if (c) document.addEventListener(eventKey, c);
                return !document[stateKey];
            }
        })();

        function getTimeRemaining(endtime) {
            var t = endtime - new **Date();**
            var seconds = Math.floor((t / 1000) % 60);
            var minutes = Math.floor((t / 1000 / 60) % 60);
            var hours = Math.floor((t / (1000 * 60 * 60)) % 24);
            return {
                'total': t,
                'hours': hours,
                'minutes': minutes,
                'seconds': seconds
            };
        }

        function initializeClock(id, endtime) {
            var clock = document.getElementById(id);
            var hoursSpan = clock.querySelector('.hours');
            var minutesSpan = clock.querySelector('.minutes');
            var secondsSpan = clock.querySelector('.seconds');
            var isPaused = true;

            vis(function(){
                document.title = vis() ? 'Visible' : 'Not visible';
                isPaused = vis() ? true : false;
            });

            function updateClock() {
                var t = getTimeRemaining(endtime);

                hoursSpan.innerHTML = ('0' + t.hours).slice(-2);
                minutesSpan.innerHTML = ('0' + t.minutes).slice(-2);
                secondsSpan.innerHTML = ('0' + t.seconds).slice(-2);

                if (t.total <= 0) {
                    clearInterval(timeinterval);
                    $.ajax({
                        url: '/myURLtoSave',
                        method: 'post',
                        data: {'rewardId': '<?php echo $video->getId(); ?>', 'page_url': '<?php echo $currentPage; ?>'},
                        response: function (result) {
                            console.log(result);
                        }
                    });
                    $('#redirect_url').attr("href", "<?php echo $pageUrl; ?>");
                    document.getElementById('redirect_url').click();
                }
            }

            updateClock();
            //var timeinterval = setInterval(updateClock, 1000);
            var timeinterval = setInterval(function(){
                if(isPaused) {
                    updateClock();
                } else {
                    //endtime = new Date(Date.parse(new Date(endtime)) + 1000);
                    //endtime = new Date(Date.parse(endtime) + 1000);
                    endtime = Date.parse(endtime) - Date.parse(new Date());
                }
            }, 1000);
        }

        var deadline = new Date(Date.parse(new Date()) + <?php echo $video->getCountdown(); ?> * 1000);
        initializeClock('clockdiv', deadline);