var timerID = null; 
var timerRunning = false; 
function showtime(element_id)
{ 
    today = new Date(); 
    BigDay = new Date("december 21, 2012") 
    msPerDay = 24 * 60 * 60 * 1000 ; 
    timeLeft = (BigDay.getTime() - today.getTime()); 
    e_daysLeft = timeLeft / msPerDay; 
    daysLeft = Math.floor(e_daysLeft); 
    e_daysLeft = timeLeft / msPerDay; 
    daysLeft = Math.floor(e_daysLeft); 
    e_hrsLeft = (e_daysLeft - daysLeft)*24; 
    hrsLeft = Math.floor(e_hrsLeft); 
    minsLeft = Math.floor((e_hrsLeft - hrsLeft)*60); 
    hrsLeft = hrsLeft; 
    e_minsLeft = (e_hrsLeft - hrsLeft)*60; 
    secLeft = Math.floor(e_hrsLeft); 
    secLeft = Math.floor((e_minsLeft - minsLeft)*60); 
    secLeft = secLeft; 

    if (secLeft < 10)
        secLeft = "0" + secLeft;

    if (minsLeft < 10)
        minsLeft = "0" + minsLeft;

    Temp3='<span class="c_days">'+daysLeft+'</span> <span class="c_day_label">dní</span>,<br/>' +
        '<span class="c_hours">'+hrsLeft+'</span> : ' +
        '<span class="c_mins">'+minsLeft+'</span> : ' +
        '<span class="c_secs">'+secLeft+'<span>';

    doc = document.getElementById(element_id);
    doc.innerHTML = Temp3;

    timerID = setTimeout("showtime('"+element_id+"')",1000); 
    timerRunning = true; 
} 

var timerID = null; 
var timerRunning = false; 

function stopclock()
{ 
    if(timerRunning) 
        clearTimeout(timerID); 
    timerRunning = false; 
} 

function stopClock()
{ 
    stopclock();     
    return; 
} 

function startclock(element_id)
{ 
    stopclock(); 
    showtime(element_id); 
}