Date Checker?

I not much of JavaScript Developer, I'm a member of the copy and paste JavaScript Generation, so perhaps someone can tell me where I'm going wrong with my function to compare two dates:

var dt1=document.booking.fromDate
var dt2=document.booking.untilDate
if (Date.parse(dt1.value) >= Date.parse(dt2.value)){
alert("Departure Date must be After Arival Date")
return false
}

return true

The problem seems to be that two date values are been compared as strings, how can I force them to be compared as dates. I thought the Date.parse() function would handle that.