[as3]Why getTime() in loop always return the same value?

programming flash
1

Hi there.i got a problem with Date.getTime()
my code like:

[COLOR=royalblue]private var now:Date = new Date();[/COLOR]

[COLOR=royalblue]private function getStamp():void{[/COLOR]
[COLOR=royalblue]trace(now.getTime());[/COLOR]
[COLOR=royalblue]setTimeout(getStamp,2000);[/COLOR]
[COLOR=royalblue]}[/COLOR]

[COLOR=black]and what i would like to do is get a different value as timestamp .[/COLOR]
Unfortunately it always trace a same value.
[COLOR=#008000]WHY? and how to solve it?[/COLOR]