Código PHP:
public function buildForm(FormBuilderInterface $builder, array $options)
{
$builder
->add('fromDate','date',array('format' => 'Y-m',
'years'=>range((date("Y")-14), date("Y")),
'label'=>'Attended from - Periodo desde'))
->add('toDate','date',array('format' => 'dd-MMM-yyyy',
'years'=>range((date("Y")-14), date("Y")),
'label'=>'Attended to - Periodo hasta'))
;
}