diff --git a/amplify/data/activity-schema.ts b/amplify/data/activity-schema.ts
index d426de91f..3761a058c 100644
--- a/amplify/data/activity-schema.ts
+++ b/amplify/data/activity-schema.ts
@@ -31,7 +31,11 @@ const activitySchema = {
       person: a.belongsTo("Person", "personId"),
       noteBlockId: a.id().required(),
       noteBlock: a.belongsTo("NoteBlock", "noteBlockId"),
+      createdAt: a.datetime().required(),
     })
+    .secondaryIndexes((index) => [
+      index("personId").sortKeys(["createdAt"]).queryField("listByPersonId"),
+    ])
     .authorization((allow) => [allow.owner()]),
   NoteBlock: a
     .model({
diff --git a/api/helpers/people.ts b/api/helpers/people.ts
index e95d84c4c..e252d8c90 100644
--- a/api/helpers/people.ts
+++ b/api/helpers/people.ts
@@ -1,4 +1,5 @@
 import { type Schema } from "@/amplify/data/resource";
+import { newDateTimeString } from "@/helpers/functional";
 import { generateClient } from "aws-amplify/api";
 const client = generateClient<Schema>();
 
@@ -9,4 +10,5 @@ export const createMentionedPersonApi = (
   client.models.NoteBlockPerson.create({
     noteBlockId,
     personId,
+    createdAt: newDateTimeString(),
   });