The example code below demonstrates how you can serialize and deserialize the date so that its object type is maintained.
// Sending the number of milliseconds since 1 January 1970 00:00:00
myDate = new Date("January 1, 2008");
dateLong = myDate.getTime();
// ~~~ Bridge ~~~
mySameDate = new Date();
Prototype methods of objects are not serialized across the interface; only the object's properties are sent.