ZF-11992

Example code:

$date1 = new Zend_Date('01/01/2012', 'dd/MM/YYYY', 'pt_BR');

var_dump($date1->toString());
var_dump($date1->toString('YYYY-MM-dd'));
var_dump($date1->toString('yyyy-MM-dd'));

$date2 = new Zend_Date('02/01/2012', 'dd/MM/YYYY', 'pt_BR');

var_dump($date2->toString());
var_dump($date2->toString('YYYY-MM-dd'));
var_dump($date2->toString('yyyy-MM-dd'));

Expected result:

// $date1
string '01/01/2012 00:00:00' (length=19)
string '2012-01-01' (length=10)
string '2012-01-01' (length=10)
// $date2
string '02/01/2012 00:00:00' (length=19)
string '2012-01-02' (length=10)
string '2012-01-02' (length=10)

Actual result:

// $date1
string '01/01/2012 00:00:00' (length=19)
string '2011-01-01' (length=10)
string '2012-01-01' (length=10)
// $date2
string '02/01/2012 00:00:00' (length=19)
string '2012-01-02' (length=10)
string '2012-01-02' (length=10)