src/Common/CreditCard.php
public function setBirthday($value)
    {
        if ($value) {
            $value = new DateTime($value, new DateTimeZone('UTC'));
        } else {
            $value = null;
        }

        return $this->setParameter('birthday', $value);
    }
public function setBirthday($value)
    {
        if ($value) {
            $value = new DateTime($value, new DateTimeZone('UTC'));
        } else {
            $value = null;
        }

        return $this->setParameter('birthday', $value);
    }
Sets the cardholder's birthday.

@param string $value
@return $this