Date field issue

I am not sure if it is only me. I have try this serveral times with date field component.

Here is my code:

<mx:Script>
	<![CDATA[
		private function init():void
		{
			text1.text = dateField.selectedDate.fullYear
			 + "/" + dateField.selectedDate.month + "/" + dateField.selectedDate.date;
		}
	]]>
</mx:Script>

<mx:Text id="text1" />

<mx:DateField id="dateField" close="init();" formatString="YYYY/MM/DD"/>

after the date field closed, the text show the right YEAR and DATE, but not the right MONTH. If I choose January, the MONTH will actually becomes to ZERO.

Please, could anyone tell me why!

Thank you so much.

Have a good festive season.