Comparing Two Dates - In And Out Values

I have the following script
function timeDifference(laterdate,earlierdate) {
var difference = laterdate.getTime() - earlierdate.getTime();
var daysDifference = Math.floor(difference/1000/60/60/24);
difference -= daysDifference*1000*60*60*24
document.write('difference = ' + daysDifference + ' day/s ');
}
var laterdate = ?;
var earlierdate = ?;
timeDifference(laterdate,earlierdate);
//--></script>

And would like to insert my datein and dateout values where the ? marks are above in red. I can call these variables into the form on the page using <%=Request("datein")%> but how do I call a variable into the script above?