src/Element/RangeFilter.php
public function getInputSpecification()
    {
        return [
            'name'       => $this->getName(),
            'required'   => false,
            'filters'    => [
                [
                    'name'    => Callback::class,
                    'options' => [
                        'callback' => function($date) {
                            // Convert the date to a specific format
                            if (is_array($date)) {
                                $date = $date['start'] . ' - ' . $date['end'];
                            }

                            return $date;
                        }
                    ]
                ]
            ],
            'validators' => []
        ];
    }
public function getInputSpecification()
    {
        return [
            'name'       => $this->getName(),
            'required'   => false,
            'filters'    => [
                [
                    'name'    => Callback::class,
                    'options' => [
                        'callback' => function($date) {
                            // Convert the date to a specific format
                            if (is_array($date)) {
                                $date = $date['start'] . ' - ' . $date['end'];
                            }

                            return $date;
                        }
                    ]
                ]
            ],
            'validators' => []
        ];
    }
Should return an array specification compatible with {@link Zend\InputFilter\Factory::createInput()}.

@return array