function show_date_time(){ 
window.setTimeout("show_date_time()", 1000); 
BirthDay=new Date("01-24-2009");//这个日期是可以修改的 
today=new Date(); 
timeold=(BirthDay.getTime()-today.getTime()); 
sectimeold=timeold/1000 
secondsold=Math.floor(sectimeold); 
msPerDay=24*60*60*1000 
e_daysold=timeold/msPerDay 
daysold=Math.floor(e_daysold); 
e_hrsold=(e_daysold-daysold)*24; 
hrsold=Math.floor(e_hrsold); 
e_minsold=(e_hrsold-hrsold)*60; 
minsold=Math.floor((e_hrsold-hrsold)*60); 
seconds=Math.floor((e_minsold-minsold)*60); 
span_dt_dt.innerHTML="<b><align=center><font  style='font-size: 10pt' color=red>"+daysold+"天"+hrsold+"小时"+minsold+"分"+seconds+"秒"+"</b></font>" ; 
} 
show_date_time();