diff --git a/src/cmd/test2json/main.go b/src/cmd/test2json/main.go
index 0c8193760f..3d7c5601a3 100644
--- a/src/cmd/test2json/main.go
+++ b/src/cmd/test2json/main.go
@@ -24,7 +24,7 @@
 // corresponding to the Go struct:
 //
 //	type TestEvent struct {
-//		Time    time.Time
+//		Time    time.Time // encodes as an RFC3339-format string
 //		Event   string
 //		Package string
 //		Test    string