diff --git a/chats/proto/chats.proto b/chats/proto/chats.proto
index e118018..41e2890 100644
--- a/chats/proto/chats.proto
+++ b/chats/proto/chats.proto
@@ -20,7 +20,7 @@ message Chat {
 	string id = 1;
 	// list of users in the chat
 	repeated string user_ids = 2;
-	// RFC3339Nano timestamp
+	// RFC3339 Nano timestamp e.g 2006-01-02T15:04:05.999999999Z07:00
 	string created_at = 3;
 }
 
@@ -33,7 +33,7 @@ message Message {
 	string chat_id = 3;
 	// text within the message
 	string text = 4;
-	// RFC3339Nano timestamp
+	// RFC3339 Nano timestamp e.g 2006-01-02T15:04:05.999999999Z07:00
 	string sent_at = 5;
 }