I know very little Javascript. I thought this would be very simple. I'm trying to have an alert pop up if someone tries to book a car between certain dates. I can't see anything wrong with this code but I don't understand the return true line. But return false didn't work either. Does date.parse put the date in MySQL format? Can anyone please tell me why it is not working? Or show me the correct way to do this? I am just adding to someone else's code. Thanks.

Code:
   date1 = document.rental.Pick_Month.value+"/"+document.rental.Pick_Day.value+"/"+document.rental.Pick_Year.value;
   date2 = document.rental.Drop_Month.value+"/"+document.rental.Drop_Day.value+"/"+document.rental.Drop_Year.value;
   date3 = (now.getMonth()+1)+"/"+now.getDate()+"/"+now.getFullYear();
   date4 = (day2.getMonth()+1)+"/"+day2.getDate()+"/"+day2.getFullYear();

   date_lim  = Date.parse(date0);
   date_num1 = Date.parse(date1);
   date_num2 = Date.parse(date2);
   date_num3 = Date.parse(date3);
   date_num4 = Date.parse(date4);

if(Pickup_Loc == "Big Island - Kona Airport" || Pickup_Loc == "Big Island - Hilo Airport") {
  if ( (date1 >= "12/24/2009" && date1 <= "12/29/2009") AND (date2 >= "12/24/2009" && date2 <= "12/29/2009") ) {
     alert("ALL CARS ARE SOLD OUT AT THIS LOCATION for Alamo, Budget, Thrifty, Avis, Dollar. We can try to arrange a car for Dec 30th or even cheaper for January 1st at regular non-Xmas Rates. For special arrangements call us at 1-888-300-7116."); 
     return true;
   }		 
}