SetInterval

var timer=null;
var aNow=null;

var g_aImg=[];
var g_oImgWeek=null;
var g_aWeekName=
[
"one",
"two",
"three",
"four",
"five",
"six",
"seven"
];

window.onload=function ()
{
var oDiv=document.getElementById('clock');
var aImg=oDiv.getElementsByTagName('img');
var i=0;

for(i=0;i<aImg.length;i++)
{
if(!isNaN(parseInt(aImg[i].alt)))
{
g_aImg.push(aImg[i]);
}
}

g_aImg.push(aImg[aImg.length-2]);

aNow=getTimeArray();

for(i=0;i<g_aImg.length;i++)
{
g_aImg[i].now=-1;
}

checkSwitch();

setInterval(checkSwitch, 1000);
checkSwitch();
}

var g_iImgHeigth=0;
var g_iTarget=0;
var g_iMax=0;

function checkSwitch()
{
var i=0;

aNow=getTimeArray();

g_imgHeigth=g_aImg[0].offsetHeight;
g_iTarget=-g_imgHeigth;
g_iMax=g_imgHeigth;

timer=setInterval(doSwitch, 30);
}

function doSwitch()
{
var bEnd=false;
var i=0;

g_imgHeigth-=5;
if(g_imgHeigth<=g_iTarget)
{
g_imgHeigth=g_iTarget;
bEnd=true;
}

for(i=0;i<g_aImg.length;i++)
{
if(g_aImg[i].now!=aNow[i])
{
if(g_imgHeigth>0)
{
g_aImg[i].style.height=g_imgHeigth+'px';
g_aImg[i].style.top=-(g_iMax-g_imgHeigth)/2+'px';
}
else
{
if(i==g_aImg.length-1)
{
g_aImg[i].src="images/" + g_aWeekName[aNow[i]] + ".png";
}
else
{
g_aImg[i].src="images/" + aNow[i] + ".png";
}

g_aImg[i].style.height=-g_imgHeigth+'px';
g_aImg[i].style.top=-(g_iMax+g_imgHeigth)/2+'px';
}
}
}

if(bEnd)
{
for(i=0;i<g_aImg.length;i++)
{
g_aImg[i].now=aNow[i];
}

clearInterval(timer);
}
}

function toDouble(iNum)
{
if(iNum<10)
{
return '0'+iNum;
}
else
{
return ''+iNum;
}
}

function getTimeArray()
{
var oDate=new Date();
var aNumber=[];

var iYear=oDate.getYear();
var iMonth=oDate.getMonth();
var iDay=oDate.getDate();
var iHour=oDate.getHours();
var iMin=oDate.getMinutes();
var iSec=oDate.getSeconds();
var iWeek=(oDate.getDay()+6)%7;

if(iYear<1900)
{
iYear+=1900;
}

var str=''+(iYear)+toDouble(iMonth+1)+toDouble(iDay)+toDouble(iHour)+toDouble(iMin)+toDouble(iSec)+iWeek;
var aChar=str.split('');

for(i=0;i<aChar.length;i++)
{
aNumber[i]=parseInt(aChar[i]);
}

return aNumber;
}