Ticket #15309: att-mod-time-patch.diff

Index: wp-includes/post.php
===================================================================
--- wp-includes/post.php        (revision 15723)
+++ wp-includes/post.php        (working copy)

@@ -3343,10 +3343,13 @@
        if ( empty($post_date_gmt) )
                $post_date_gmt = current_time('mysql', 1);
 
-       if ( empty($post_modified) )
-               $post_modified = $post_date;
-       if ( empty($post_modified_gmt) )
+       if ( $update || '0000-00-00 00:00:00' == $post_date ) {
+               $post_modified     = current_time( 'mysql' );
+               $post_modified_gmt = current_time( 'mysql', 1 );
+       } else {
+               $post_modified     = $post_date;
                $post_modified_gmt = $post_date_gmt;
+       }
 
        if ( empty($comment_status) ) {
                if ( $update )