Index: modules/system/system.api.php
===================================================================
RCS file: /cvs/drupal/drupal/modules/system/system.api.php,v
retrieving revision 1.151
diff -u -r1.151 system.api.php
--- modules/system/system.api.php	10 Apr 2010 17:30:15 -0000	1.151
+++ modules/system/system.api.php	19 Apr 2010 00:02:55 -0000
@@ -2817,6 +2817,29 @@
 }
 
 /**
+ * Modify existing date format types.
+ * 
+ * Allows other modules to modify existing date types like 'long'.  Called
+ * by _system_date_format_types_build().  A module may use this hook to apply
+ * settings across all date types. For example, the module could lock all date 
+ * types so they appear to be provided by the system.
+ * 
+ * @param $types 
+ *   An associative array of date types containing:
+ *   - types:  an array of date format types including configuration settings for each type:
+ *     - is_new: Set to FALSE to override previous settings
+ *     - module: the name of the module that created the date type
+ *     - type: the date type name
+ *     - title: the title of the date type
+ *     - locked: specifies that the date type is system provided
+ */
+function hook_date_format_types_alter(&$types) {
+	foreach ($types as $type_name => $type) {
+		$type['locked'] = 1;
+	}
+}
+
+/**
  * Defines additional date formats.
  *
  * Next to the 'long', 'medium' and 'short' date types defined in core, any