Date CCK Field in View Table Not Sortable

I just noticed that in my implementation, a CCK Date field can not be made sortable in a Views table. See attached.

Is this a cck date field rule, or is there a configuration which will allow cck date fields to be sortable in a Views table? Below is an export of the view in question. Thanks for any assistance.

php version: PHP 5.1.6
php4.module enabled?: Yes
Export of content type and cck date fields: attached

$view = new view;
$view->name = 'EventsTest';
$view->description = 'Test View for Events';
$view->tag = 'events';
$view->view_php = '';
$view->base_table = 'node';
$view->is_cacheable = FALSE;
$view->api_version = 2;
$view->disabled = FALSE; /* Edit this to true to make a default view disabled initially */
$handler = $view->new_display('default', 'Defaults', 'default');
$handler->override_option('fields', array(
  'title' => array(
    'label' => 'Title',
    'alter' => array(
      'alter_text' => 0,
      'text' => '',
      'make_link' => 0,
      'path' => '',
      'link_class' => '',
      'alt' => '',
      'prefix' => '',
      'suffix' => '',
      'help' => '',
      'trim' => 0,
      'max_length' => '',
      'word_boundary' => 1,
      'ellipsis' => 1,
      'strip_tags' => 0,
      'html' => 0,
    ),
    'link_to_node' => 1,
    'exclude' => 0,
    'id' => 'title',
    'table' => 'node',
    'field' => 'title',
    'relationship' => 'none',
  ),
  'field_eventstart_value' => array(
    'label' => 'Start date',
    'alter' => array(
      'alter_text' => 0,
      'text' => '',
      'make_link' => 0,
      'path' => '',
      'link_class' => '',
      'alt' => '',
      'prefix' => '',
      'suffix' => '',
      'help' => '',
      'trim' => 0,
      'max_length' => '',
      'word_boundary' => 1,
      'ellipsis' => 1,
      'strip_tags' => 0,
      'html' => 0,
    ),
    'link_to_node' => 0,
    'label_type' => 'widget',
    'format' => 'short',
    'multiple' => array(
      'multiple_number' => '',
      'multiple_from' => '',
      'multiple_to' => '',
      'group' => 1,
    ),
    'repeat' => array(
      'show_repeat_rule' => 'show',
    ),
    'fromto' => array(
      'fromto' => 'value',
    ),
    'exclude' => 0,
    'id' => 'field_eventstart_value',
    'table' => 'node_data_field_eventstart',
    'field' => 'field_eventstart_value',
    'relationship' => 'none',
  ),
  'field_teststart_value' => array(
    'label' => 'Test date',
    'alter' => array(
      'alter_text' => 0,
      'text' => '',
      'make_link' => 0,
      'path' => '',
      'link_class' => '',
      'alt' => '',
      'prefix' => '',
      'suffix' => '',
      'help' => '',
      'trim' => 0,
      'max_length' => '',
      'word_boundary' => 1,
      'ellipsis' => 1,
      'strip_tags' => 0,
      'html' => 0,
    ),
    'link_to_node' => 0,
    'label_type' => 'widget',
    'format' => 'default',
    'multiple' => array(
      'multiple_number' => '',
      'multiple_from' => '',
      'multiple_to' => '',
      'group' => 1,
    ),
    'repeat' => array(
      'show_repeat_rule' => 'hide',
    ),
    'fromto' => array(
      'fromto' => 'both',
    ),
    'exclude' => 0,
    'id' => 'field_teststart_value',
    'table' => 'node_data_field_teststart',
    'field' => 'field_teststart_value',
    'relationship' => 'none',
  ),
));
$handler->override_option('sorts', array(
  'created' => array(
    'id' => 'created',
    'table' => 'node',
    'field' => 'created',
    'order' => 'DESC',
    'granularity' => 'second',
  ),
));
$handler->override_option('filters', array(
  'type' => array(
    'id' => 'type',
    'table' => 'node',
    'field' => 'type',
    'operator' => 'in',
    'value' => array(
      '0' => 'event',
    ),
  ),
  'status' => array(
    'id' => 'status',
    'table' => 'node',
    'field' => 'status',
    'value' => '1',
  ),
  'date_filter' => array(
    'operator' => '<',
    'value' => array(
      'value' => NULL,
      'min' => NULL,
      'max' => NULL,
      'default_date' => 'now',
      'default_to_date' => '',
    ),
    'group' => '0',
    'exposed' => FALSE,
    'expose' => array(
      'operator' => FALSE,
      'label' => '',
    ),
    'date_fields' => array(
      'node_data_field_eventstart.field_eventstart_value' => 'node_data_field_eventstart.field_eventstart_value',
    ),
    'date_method' => 'OR',
    'granularity' => 'day',
    'form_type' => 'date_select',
    'default_date' => 'now',
    'default_to_date' => '',
    'year_range' => '-3:+3',
    'id' => 'date_filter',
    'table' => 'node',
    'field' => 'date_filter',
    'relationship' => 'none',
  ),
));
$handler->override_option('access', array(
  'type' => 'none',
  'role' => array(),
  'perm' => '',
));
$handler->override_option('cache', array(
  'type' => 'none',
));
$handler->override_option('title', 'Test Events');
$handler->override_option('header_format', '1');
$handler->override_option('footer_format', '1');
$handler->override_option('empty_format', '1');
$handler->override_option('items_per_page', '30');
$handler->override_option('use_pager', '1');
$handler->override_option('distinct', 0);
$handler->override_option('style_plugin', 'table');
$handler->override_option('style_options', array(
  'grouping' => '',
  'override' => 0,
  'sticky' => 0,
  'order' => 'asc',
  'columns' => array(
    'title' => 'title',
    'field_eventstart_value' => 'field_eventstart_value',
    'field_teststart_value' => 'field_teststart_value',
  ),
  'info' => array(
    'title' => array(
      'sortable' => 1,
      'separator' => '',
    ),
    'field_eventstart_value' => array(
      'separator' => '',
    ),
    'field_teststart_value' => array(
      'separator' => '',
    ),
  ),
  'default' => '-1',
));
$handler = $view->new_display('page', 'Page', 'page_1');
$handler->override_option('path', 'view/test/events');
$handler->override_option('menu', array(
  'type' => 'none',
  'title' => '',
  'description' => '',
  'weight' => 0,
  'name' => 'navigation',
));
$handler->override_option('tab_options', array(
  'type' => 'none',
  'title' => '',
  'description' => '',
  'weight' => 0,
));