diff --git a/src/undo.c b/src/undo.c
index af91bd3..998f3f3 100644
--- a/src/undo.c
+++ b/src/undo.c
@@ -2884,7 +2884,7 @@
 	    (void)strftime((char *)buf, buflen, "%m/%d %H:%M:%S", curtime);
 	else
 	    /* long ago */
-	    (void)strftime((char *)buf, buflen, "%y/%m/%d %H:%M:%S", curtime);
+	    (void)strftime((char *)buf, buflen, "%Y/%m/%d %H:%M:%S", curtime);
     }
     else
 #endif