Index: export.php
===================================================================
--- export.php	(revision 30735)
+++ export.php	(working copy)
@@ -76,6 +76,13 @@
 		if ( $args['author'] )
 			$where .= $wpdb->prepare( " AND {$wpdb->posts}.post_author = %d", $args['author'] );
 
+        // Swap start and end dates if, and only if, start date is more recent than end date
+        if ( $args['start_date'] && $args['end_date'] && $args['start_date'] > $args['end_date'] ) {
+            $swap = $args['start_date'];
+            $args['start_date'] = $args['end_date'];
+            $args['end_date'] = $swap;
+        }
+
 		if ( $args['start_date'] )
 			$where .= $wpdb->prepare( " AND {$wpdb->posts}.post_date >= %s", date( 'Y-m-d', strtotime($args['start_date']) ) );