add vttimefmt
diff --git a/include/venti.h b/include/venti.h
index c4538a9..9fea5bc 100644
--- a/include/venti.h
+++ b/include/venti.h
@@ -488,6 +488,8 @@
 int vtfilesetsize(VtFile*, u64int);
 int vtfileremove(VtFile*);
 
+extern int vttimefmt(Fmt*);
+
 extern int chattyventi;
 extern int ventidoublechecksha1;
 extern int ventilogging;