Duplicate ID error when using the date filter multiple times on the same view

Here is a patch using the proposed solution of using the $identifier parameter instead of the object "field" value.

I am updating the title and description to clarify the issue.

Here is a basic view that could be used to test the issue. In the view we add the date filter twice (one to filter on post date and another for the updated date).

I tested the patch and it fixes the issue for me.

$view = new view();
$view->name = 'date_filter_test';
$view->description = '';
$view->tag = 'default';
$view->base_table = 'node';
$view->human_name = 'Date filter test';
$view->core = 7;
$view->api_version = '3.0';
$view->disabled = FALSE; /* Edit this to true to make a default view disabled initially */

/* Display: Master */
$handler = $view->new_display('default', 'Master', 'default');
$handler->display->display_options['title'] = 'Date filter test';
$handler->display->display_options['use_more_always'] = FALSE;
$handler->display->display_options['access']['type'] = 'perm';
$handler->display->display_options['cache']['type'] = 'none';
$handler->display->display_options['query']['type'] = 'views_query';
$handler->display->display_options['exposed_form']['type'] = 'basic';
$handler->display->display_options['pager']['type'] = 'none';
$handler->display->display_options['style_plugin'] = 'table';
/* Field: Content: Title */
$handler->display->display_options['fields']['title']['id'] = 'title';
$handler->display->display_options['fields']['title']['table'] = 'node';
$handler->display->display_options['fields']['title']['field'] = 'title';
$handler->display->display_options['fields']['title']['alter']['word_boundary'] = FALSE;
$handler->display->display_options['fields']['title']['alter']['ellipsis'] = FALSE;
/* Field: Content: Post date */
$handler->display->display_options['fields']['created']['id'] = 'created';
$handler->display->display_options['fields']['created']['table'] = 'node';
$handler->display->display_options['fields']['created']['field'] = 'created';
$handler->display->display_options['fields']['created']['date_format'] = 'long';
$handler->display->display_options['fields']['created']['second_date_format'] = 'long';
/* Field: Content: Updated date */
$handler->display->display_options['fields']['changed']['id'] = 'changed';
$handler->display->display_options['fields']['changed']['table'] = 'node';
$handler->display->display_options['fields']['changed']['field'] = 'changed';
$handler->display->display_options['fields']['changed']['date_format'] = 'long';
$handler->display->display_options['fields']['changed']['second_date_format'] = 'long';
/* Sort criterion: Content: Title */
$handler->display->display_options['sorts']['title']['id'] = 'title';
$handler->display->display_options['sorts']['title']['table'] = 'node';
$handler->display->display_options['sorts']['title']['field'] = 'title';
$handler->display->display_options['sorts']['title']['order'] = 'DESC';
/* Filter criterion: Content: Published status */
$handler->display->display_options['filters']['status']['id'] = 'status';
$handler->display->display_options['filters']['status']['table'] = 'node';
$handler->display->display_options['filters']['status']['field'] = 'status';
$handler->display->display_options['filters']['status']['value'] = 1;
$handler->display->display_options['filters']['status']['group'] = 1;
$handler->display->display_options['filters']['status']['expose']['operator'] = FALSE;
/* Filter criterion: Content: Type */
$handler->display->display_options['filters']['type']['id'] = 'type';
$handler->display->display_options['filters']['type']['table'] = 'node';
$handler->display->display_options['filters']['type']['field'] = 'type';
$handler->display->display_options['filters']['type']['value'] = array(
  'page' => 'page',
);
/* Filter criterion: Date: Date (node) */
$handler->display->display_options['filters']['date_filter']['id'] = 'date_filter';
$handler->display->display_options['filters']['date_filter']['table'] = 'node';
$handler->display->display_options['filters']['date_filter']['field'] = 'date_filter';
$handler->display->display_options['filters']['date_filter']['operator'] = 'between';
$handler->display->display_options['filters']['date_filter']['exposed'] = TRUE;
$handler->display->display_options['filters']['date_filter']['expose']['operator_id'] = 'date_filter_op';
$handler->display->display_options['filters']['date_filter']['expose']['label'] = 'Filter by post date';
$handler->display->display_options['filters']['date_filter']['expose']['use_operator'] = TRUE;
$handler->display->display_options['filters']['date_filter']['expose']['operator'] = 'date_filter_op';
$handler->display->display_options['filters']['date_filter']['expose']['identifier'] = 'date_filter';
$handler->display->display_options['filters']['date_filter']['expose']['remember_roles'] = array(
  2 => '2',
);
$handler->display->display_options['filters']['date_filter']['date_fields'] = array(
  'node.created' => 'node.created',
);
/* Filter criterion: Date: Date (node) */
$handler->display->display_options['filters']['date_filter_1']['id'] = 'date_filter_1';
$handler->display->display_options['filters']['date_filter_1']['table'] = 'node';
$handler->display->display_options['filters']['date_filter_1']['field'] = 'date_filter';
$handler->display->display_options['filters']['date_filter_1']['operator'] = 'between';
$handler->display->display_options['filters']['date_filter_1']['exposed'] = TRUE;
$handler->display->display_options['filters']['date_filter_1']['expose']['operator_id'] = 'date_filter_1_op';
$handler->display->display_options['filters']['date_filter_1']['expose']['label'] = 'Filter by updated date';
$handler->display->display_options['filters']['date_filter_1']['expose']['use_operator'] = TRUE;
$handler->display->display_options['filters']['date_filter_1']['expose']['operator'] = 'date_filter_1_op';
$handler->display->display_options['filters']['date_filter_1']['expose']['identifier'] = 'date_filter_1';
$handler->display->display_options['filters']['date_filter_1']['expose']['remember_roles'] = array(
  2 => '2',
);
$handler->display->display_options['filters']['date_filter_1']['date_fields'] = array(
  'node.changed' => 'node.changed',
);

/* Display: Page */
$handler = $view->new_display('page', 'Page', 'page');
$handler->display->display_options['path'] = 'date-filter-test';