diff --git a/README.md b/README.md
index 5259709..01881f3 100644
--- a/README.md
+++ b/README.md
@@ -61,3 +61,5 @@ To generate events as fast as possible ...
             nevents += len(e)
 
         now = g.move_to_next_tick(now)
+
+Datetimes are returned as strings as OpenStack would.