function countDown(num) {      
work_number = time_diff[num]--;
if (work_number<0) {document.getElementById('counter'+num).innerHTML = 'АКЦИЯ ЗАКОНЧЕНА'; } else {
days = Math.floor(work_number / 86400);      
work_number -= days * 86400;
hours = Math.floor(work_number / 3600);
work_number -= hours * 3600;
minutes = Math.floor(work_number / 60);
work_number -= minutes * 60;
seconds = Math.floor(work_number % 60);
days = (days < 10) ? "0"+days : days;
hours = (hours < 10) ? "0"+hours : hours;
minutes = (minutes < 10) ? "0"+minutes : minutes;
seconds = (seconds < 10) ? "0"+seconds : seconds;
values = [
declOfNum(days, ["день", "дня", "дней"]), 
declOfNum(hours, ["час", "часа", "часов"]),  //
declOfNum(minutes, ["минута", "минуты", "минут"]),  //
declOfNum(seconds, ["секунда", "секунды", "секунд"]) //
];
document.getElementById('counter'+num).innerHTML =  values.join(" ");// + ".";      
}
}

function declOfNum(number, titles) {
cases = [2, 0, 1, 1, 1, 2];
return "<b>" + number + "</b> " + titles[ (number%100>4 && number%100<20)? 2 : cases[Math.min(number%10, 5)] ];
}