Strange things happening

Running the function below gives:

Current date--> Sat Jul 11 01:35:36 GMT+0200 2009
Due date------> Thu Jan 1 15:53:40 GMT+0200 2009
Days overdue--> 41

The Days overdue are NOT 41 (from Jan 15, 2009 to July 11,2009).

What am I doing wrong?

function overDueBy(dueDate:Date):String{

   var millisecondsPerDay:int = 1000 * 60 * 60 * 24;

   var milliseconds:uint= ((new Date()).getTime() - dueDate.getTime());

   trace("Current date--> "+new Date());

   trace("Due date------> "+dueDate);

   trace("Days overdue--> "+Math.round(milliseconds/(millisecondsPerDay)));

  }