Admin datetime picker returning empty array on post

Question

I have a custom admin edit form with the following fields:

$dateTimeFormatIso = Mage::app()->getLocale()->getDateTimeFormat(Mage_Core_Model_Locale::FORMAT_TYPE_SHORT);
$fieldsetRefInfo->addField('start_date', 'date', array(
    'name' => 'start_date',
    'input_format' => Varien_Date::DATETIME_INTERNAL_FORMAT,
    'format' => $dateTimeFormatIso,
    'time' => true,
    'image' => $this->getSkinUrl('images/grid-cal.gif'),
    'required' => true,
    'label' => Mage::helper('vendor_module')->__('Start Date'),
    'title' => Mage::helper('vendor_module')->__('Start Date'),
    'style' => 'width: 120px',
));
$fieldsetRefInfo->addField('expire_date', 'date', array(
    'name' => 'expire_date',
    'input_format' => Varien_Date::DATETIME_INTERNAL_FORMAT,
    'format' => $dateTimeFormatIso,
    'time' => true,
    'image' => $this->getSkinUrl('images/grid-cal.gif'),
    'required' => true,
    'label' => Mage::helper('vendor_module')->__('Expiration Date'),
    'title' => Mage::helper('vendor_module')->__('Expiration Date'),
    'style' => 'width: 120px',
));

When I get the data back in my controller upon save, the start_date field comes back as string, but the expire_date field comes back as an array with no values:

$data['start_date'] = '3/5/18 5:46 PM';
$data['expire_date'] = ['from' => '', 'to' => '', 'local' => 'en_US'];

I'm assuming there's some JS going on in the background that is transforming the data, since the $_POST data comes back the same way.

Any ideas as to where I can start looking for this data transformation?

[EDIT - Here is the full form code]

protected function _prepareForm()
{
    $form = new Varien_Data_Form();
    $form->setHtmlIdPrefix('subscription_');

    $formData = $this->_getFormData();

    $fieldsetRefInfo = $form->addFieldset('vendor_module_reference_info', array(
        'legend' => Mage::helper('vendor_module')->__('Subscription Information')
    ));

    $fieldsetRefInfo->addField('status', 'label', array(
        'label' => Mage::helper('vendor_module')->__('Status'),
        'title' => Mage::helper('vendor_module')->__('Status'),
        'name' => 'status',
    ));

    $fieldsetRefInfo->addType('converted_date', 'Vendor_Module_Block_Adminhtml_Sales_Subscription_Edit_Element_Datetime');
    $fieldsetRefInfo->addField('created_at', 'converted_date', array(
        'name' => 'created_at',
        'label' => Mage::helper('vendor_module')->__('Created Date'),
        'title' => Mage::helper('vendor_module')->__('Created Date'),
    ));

    $dateTimeFormatIso = Mage::app()->getLocale()->getDateTimeFormat(Mage_Core_Model_Locale::FORMAT_TYPE_SHORT);
    $fieldsetRefInfo->addField('start_date', 'date', array(
        'name' => 'start_date',
        'input_format' => Varien_Date::DATETIME_INTERNAL_FORMAT,
        'format' => $dateTimeFormatIso,
        'time' => true,
        'image' => $this->getSkinUrl('images/grid-cal.gif'),
        'required' => true,
        'label' => Mage::helper('vendor_module')->__('Start Date'),
        'title' => Mage::helper('vendor_module')->__('Start Date'),
        'style' => 'width: 120px',
    ));
    $fieldsetRefInfo->addField('expire_date', 'date', array(
        'name' => 'expire_date',
        'input_format' => Varien_Date::DATETIME_INTERNAL_FORMAT,
        'format' => $dateTimeFormatIso,
        'time' => true,
        'image' => $this->getSkinUrl('images/grid-cal.gif'),
        'required' => true,
        'label' => Mage::helper('vendor_module')->__('Expiration Date'),
        'title' => Mage::helper('vendor_module')->__('Expiration Date'),
        'style' => 'width: 120px',
    ));

    // customer info
    $fieldsetCustomer = $form->addFieldset('vendor_module_customer_info', array(
        'legend' => Mage::helper('vendor_module')->__('Customer Information')
    ));

    $fieldsetCustomer->addField('customer_id', 'label', array(
        'label' => Mage::helper('vendor_module')->__('Customer ID'),
        'title' => Mage::helper('vendor_module')->__('Customer ID'),
        'name' => 'customer_id',
    ));

    $customerLink = Mage::helper('adminhtml')->getUrl(
        'adminhtml/customer/edit',
        array('id' => $formData['customer_id'])
    );
    $fieldsetCustomer->addField('customer_name', 'link', array(
        'label' => Mage::helper('vendor_module')->__('Name'),
        'title' => Mage::helper('vendor_module')->__('Name'),
        'name' => 'customer_name',
        'href' => $customerLink,
    ));

    // product info
    $fieldsetProduct = $form->addFieldset('vendor_module_product', array(
        'legend' => Mage::helper('vendor_module')->__('Product Details')
    ));

    $productLink = Mage::helper('adminhtml')->getUrl(
        'adminhtml/catalog_product/view',
        array('product_id' => $formData['final_product_id'])
    );

    $fieldsetProduct->addField('product_sku', 'label', array(
        'label' => Mage::helper('vendor_module')->__('SKU'),
        'title' => Mage::helper('vendor_module')->__('SKU'),
        'name' => 'product_sku',
    ));

    $form->addValues($formData);
    $this->setForm($form);
    return parent::_prepareForm();
}

Answer 1

Make sure you don't have any other tabs in the form that are POSTing with the same input name as "expire_date".