Index: wp-includes/taxonomy.php
===================================================================
--- wp-includes/taxonomy.php	(revision 23356)
+++ wp-includes/taxonomy.php	(working copy)
@@ -1240,10 +1240,10 @@
 	// $args can be whatever, only use the args defined in defaults to compute the key
 	$filter_key = ( has_filter('list_terms_exclusions') ) ? serialize($GLOBALS['wp_filter']['list_terms_exclusions']) : '';
 	$key = md5( serialize( compact(array_keys($defaults)) ) . serialize( $taxonomies ) . $filter_key );
-	$last_changed = wp_cache_get('last_changed', 'terms');
-	if ( !$last_changed ) {
-		$last_changed = time();
-		wp_cache_set('last_changed', $last_changed, 'terms');
+	$last_changed = wp_cache_get( 'last_changed', 'terms' );
+	if ( ! $last_changed ) {
+		$last_changed = 1;
+		wp_cache_set( 'last_changed', $last_changed, 'terms' );
 	}
 	$cache_key = "get_terms:$key:$last_changed";
 	$cache = wp_cache_get( $cache_key, 'terms' );
@@ -2632,7 +2632,12 @@
 		do_action('clean_term_cache', $ids, $taxonomy);
 	}
 
-	wp_cache_set('last_changed', time(), 'terms');
+	if ( function_exists( 'wp_cache_incr' ) ) {
+		wp_cache_incr( 'last_changed', 1, 'terms' );
+	} else {
+		$last_changed = wp_cache_get( 'last_changed', 'terms' );
+		wp_cache_set( 'last_changed', $last_changed + 1, 'terms' );
+	}
 }
 
 /**