[flexcoders] why "disabledRanges" doesn't work

[markflex2007]

I set the  disabledRanges for DateField,but I can select any date,it seems 
"disabledRanges" doesn't work.

Please help.Thanks


<mx:DateField id="checkedDate" x="81" y="108" formatString="YYYY-MM-DD" 
width="121"   disabledRanges="{[{rangeStart: new Date(2010,2,1)}]}"  />