[рони]

denik,
остальные месяцы допишите сами

<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.12.0/jquery.min.js"></script>

<div id="CountdownClock"><div id="CountdownClockHTML"><span class="daysLeft"></span><span class="timeLeft"></span></div></div>


<script>   time_to_x_hour = false;

function PremierTimer(premiere_date) {
    if (premiere_date) {
        premiere_date = premiere_date.replace(/[а-яё]+/gi, function(a) {
            return {
                'января': 'January',
                'февраля': 'February'
            }[a] || a
        })
        var now = new Date();
        var premiere = new Date(premiere_date);
        time_to_x_hour = (premiere.getTime() - now.getTime()) / 1000;
    }

    if (time_to_x_hour <= 0) {

        if (document.getElementById('CountdownClockDiv'))
            document.getElementById('CountdownClockDiv').style.display = "none";
        document.getElementById('CountdownClock').innerHTML = "Событие состоялась";
        return;
    }
    var daysleft = parseInt(time_to_x_hour / (24 * 60 * 60));

    if (daysleft < 0) daysleft = 0;
    var d = daysleft - Math.floor(daysleft / 10) * 10;
    var dd = 0;
    if (daysleft > 100) dd = daysleft - Math.floor(daysleft / 100) * 100;
    var daysleftFinal;
    var text_day;
    if (d == 1 && daysleft != 11 && dd != 11) text_day = "День ";
    else if (d > 1 && d < 5 && (daysleft < 10 || daysleft > 20) && (!dd || dd > 20 || dd < 5)) text_day = "Дня ";
    else if (d >= 0) text_day = "Дней ";
    if (daysleft > 0) daysleftFinal = 'Событие через<br /><span class="daysLeft">' + daysleft + '&nbsp;' + text_day + '</span><span class="timeLeft">+';
    else daysleftFinal = '';



    var hours = parseInt((time_to_x_hour - daysleft * (24 * 60 * 60)) / (60 * 60));
    var minutes = parseInt((time_to_x_hour - daysleft * (24 * 60 * 60) - hours * (60 * 60)) / 60);
    var seconds = parseInt(time_to_x_hour - daysleft * (24 * 60 * 60) - hours * (60 * 60) - minutes * 60);
    hours = hours.toString().length > 1 ? hours : "0" + hours;
    minutes = minutes.toString().length > 1 ? minutes : "0" + minutes;
    seconds = seconds.toString().length > 1 ? seconds : "0" + seconds;
    time_to_x_hour--;
    if (!document.getElementById('CountdownClockHTML'))
        document.getElementById('CountdownClock').innerHTML = "<div id='CountdownClockHTML'></div>";
    if (document.getElementById('CountdownClockHTML'))
        document.getElementById('CountdownClockHTML').innerHTML = (daysleftFinal) +
        hours + ':' +
        minutes + ':' +
        seconds + '</span>';

    setTimeout(function() {
        PremierTimer();
    }, 1000);
}</script>


<script>$(function(){ PremierTimer('16 февраля 2020,00:00:00'); });</script>