diff --git a/src/timestamp.mli b/src/timestamp.mli
index e308e960..c3bc216a 100644
--- a/src/timestamp.mli
+++ b/src/timestamp.mli
@@ -1,3 +1,6 @@
+(* TODO time
+   not sure about this *)
+
 type t = Ptime.t option
 
 val jsont : t Jsont.t