diff --git a/date.install b/date.install
index 9a9b6d3..aa71008 100644
--- a/date.install
+++ b/date.install
@@ -51,6 +51,19 @@ function date_field_schema($field) {
     // We don't want Field API to create additional columns, just the first.
     // We modify them our own way in views data.
     $db_columns['value2']['views'] = FALSE;
+
+    // If the end date is optional, we need an extra field to know when the end
+    // date is really filled.
+    if ($field['settings']['todate'] === 'optional') {
+      $db_columns['has_todate'] = array(
+        'type' => 'int',
+        'size' => 'tiny',
+        'not null' => TRUE,
+        'default' => 0,
+        'sortable' => TRUE,
+        'views' => TRUE,
+      );
+    }
   }
   // Timezone and offset columns are used only if date-specific dates are used.
   if (isset($field['settings']['tz_handling']) && $field['settings']['tz_handling'] == 'date') {
@@ -204,3 +217,50 @@ function date_update_7004() {
   field_cache_clear();
   drupal_set_message(t('Date text widgets have been updated to use an increment of 1.'));
 }
+
+/**
+ * Add the has_todate column to all fields that have optional end date.
+ */
+function date_update_7005() {
+  $tables = array();
+  $column = array(
+    'type' => 'int',
+    'size' => 'tiny',
+    'not null' => TRUE,
+    'default' => 0,
+    'sortable' => TRUE,
+    'views' => TRUE,
+  );
+
+  foreach (field_info_fields() as $field) {
+    if ($field['module'] === 'date') {
+      if (!empty($field['settings']['todate']) && $field['settings']['todate'] === 'optional') {
+        $has_todate = _field_sql_storage_columnname($field['field_name'], 'has_todate');
+        $tables[$field['field_name']] = array(
+          _field_sql_storage_tablename($field),
+          _field_sql_storage_revision_tablename($field),
+        );
+
+        foreach ($tables[$field['field_name']] as $table) {
+          db_add_field($table, $has_todate, $column);
+        }
+      }
+    }
+  }
+
+  field_cache_clear();
+  drupal_get_schema(NULL, TRUE);
+
+  // Now it is time to update the values of the new column.
+  foreach ($tables as $field_name => $ts) {
+    foreach ($ts as $table) {
+      $value = _field_sql_storage_columnname($field_name, 'value');
+      $value2 = _field_sql_storage_columnname($field_name, 'value2');
+      $has_todate = _field_sql_storage_columnname($field_name, 'has_todate');
+
+      // Update the value of this new column. Make use of db_query to take
+      // care of large sites that makes a huge usage of date fields.
+      db_query("UPDATE {{$table}} SET `$has_todate` = :to_date WHERE `$value` != `$value2`", array(':to_date' => 1));
+    }
+  }
+}
diff --git a/date_elements.inc b/date_elements.inc
index b99f2c3..61cd7b7 100644
--- a/date_elements.inc
+++ b/date_elements.inc
@@ -532,11 +532,16 @@ function date_combo_validate($element, &$form_state) {
     }
   }
 
-  // If the user chose the option to not show the end date, just swap in the
-  // start date as that value so the start and end dates are the same.
-  if ($field['settings']['todate'] == 'optional' && empty($item['show_todate'])) {
-    $item[$to_field] = $item[$from_field];
-    $posted[$to_field] = $posted[$from_field];
+  if ($field['settings']['todate'] == 'optional') {
+    $item['has_todate'] = 1;
+
+    // If the user chose the option to not show the end date, just swap in the
+    // start date as that value so the start and end dates are the same.
+    if (empty($item['show_todate'])) {
+      $item[$to_field] = $item[$from_field];
+      $posted[$to_field] = $posted[$from_field];
+      $item['has_todate'] = 0;
+    }
   }
 
   if ($empty) {