Index: wp-includes/class-wp-date-query.php
===================================================================
--- wp-includes/class-wp-date-query.php	(revision 54316)
+++ wp-includes/class-wp-date-query.php	(working copy)
@@ -472,6 +472,8 @@
 	 * check, and are only sanitized to remove illegal characters.
 	 *
 	 * @since 3.7.0
+	 * 
+	 * @global wpdb $wpdb WordPress database abstraction object.
 	 *
 	 * @param string $column The user-supplied column name.
 	 * @return string A validated column name value.
@@ -698,6 +700,8 @@
 	 * Turns a first-order date query into SQL for a WHERE clause.
 	 *
 	 * @since 4.1.0
+	 * 
+	 * @global wpdb $wpdb WordPress database abstraction object.
 	 *
 	 * @param array $query        Date query clause.
 	 * @param array $parent_query Parent query of the current date query.
@@ -960,6 +964,8 @@
 	 * in order to be able to accurately compare against.
 	 *
 	 * @since 3.7.0
+	 * 
+	 * @global wpdb $wpdb WordPress database abstraction object.
 	 *
 	 * @param string   $column  The column to query against. Needs to be pre-validated!
 	 * @param string   $compare The comparison operator. Needs to be pre-validated!