function validate_dates()
{
    valid = true;
    var today = new Date();
    today = new Date(today.getFullYear(),today.getMonth(),today.getDate());
    var ayear = document.dates.ayear.value;
    var amonth = parseInt(document.dates.amonth.value)-1;
    var aday = parseInt(document.dates.aday.value);
    var dyear = document.dates.dyear.value;
    var dmonth = parseInt(document.dates.dmonth.value)-1;
    var dday = parseInt(document.dates.dday.value);
    var adt = new Date(ayear,amonth,aday,20);
    var ddt = new Date(dyear,dmonth,dday);

    if (adt <= today)
    {
        alert( "It appears that your arrival date has already gone by." );
        valid = false;
    }

    if (ddt <= adt)
    {
        alert ( "Please choose a departure date that is after you're arrival date." );
        valid = false;
    }

    return valid;
}