diff --git a/lambda/onMessage.ts b/lambda/onMessage.ts
index 9fb4f15..9a6c109 100644
--- a/lambda/onMessage.ts
+++ b/lambda/onMessage.ts
@@ -123,7 +123,7 @@ export const handler = async (
 
 	if (message.data === 'LWM2M-shadows') {
 		// Publish LwM2M shadows
-		const shadows = await fetchLwM2M()
+		const shadows = await fetchLwM2M(1)
 
 		console.log(
 			JSON.stringify({
diff --git a/lambda/publishLwM2MShadowsToJSON.ts b/lambda/publishLwM2MShadowsToJSON.ts
index 82cf3cc..6e899ec 100644
--- a/lambda/publishLwM2MShadowsToJSON.ts
+++ b/lambda/publishLwM2MShadowsToJSON.ts
@@ -17,7 +17,7 @@ export const handler = async (): Promise<void> => {
 			CacheControl: 'public, max-age=60',
 			Body: JSON.stringify({
 				'@context': 'https://github.com/hello-nrfcloud/proto/map/devices',
-				devices: (await fetchShadows()).map(({ deviceId, objects }) => ({
+				devices: (await fetchShadows(30)).map(({ deviceId, objects }) => ({
 					'@context': 'https://github.com/hello-nrfcloud/proto/map/device',
 					id: deviceId,
 					model: 'world.thingy.rocks',
diff --git a/lwm2m/fetchLwM2MShadows.ts b/lwm2m/fetchLwM2MShadows.ts
index fce5c60..433e954 100644
--- a/lwm2m/fetchLwM2MShadows.ts
+++ b/lwm2m/fetchLwM2MShadows.ts
@@ -2,6 +2,7 @@ import { IoTClient, SearchIndexCommand } from '@aws-sdk/client-iot'
 import type { LwM2MObjectInstance } from '@hello.nrfcloud.com/proto-lwm2m'
 import { shadowToObjects } from './shadowToObjects.js'
 import { getDeviceInfo } from '../lambda/withDeviceAlias.js'
+import { instanceTs } from './instanceTs.js'
 
 type LwM2MShadow = {
 	deviceId: string
@@ -11,9 +12,9 @@ type LwM2MShadow = {
 
 export const fetchLwM2MShadows = (
 	iot: IoTClient,
-): (() => Promise<LwM2MShadow[]>) => {
+): ((notOlderThanDays?: number) => Promise<LwM2MShadow[]>) => {
 	const deviceInfo = getDeviceInfo(iot)
-	return async () => {
+	return async (notOlderThanDays = 30) => {
 		const { things } = await iot.send(
 			new SearchIndexCommand({
 				// Find all things which have an LwM2M shadow
@@ -36,7 +37,13 @@ export const fetchLwM2MShadows = (
 						return {
 							deviceId: thingName as string,
 							alias,
-							objects: shadowToObjects(reported),
+							objects: shadowToObjects(reported).filter((instance) => {
+								const updateTs = instanceTs(instance)
+								return (
+									Date.now() - updateTs.getTime() <
+									notOlderThanDays * 24 * 60 * 60 * 1000
+								)
+							}),
 						}
 					} catch (err) {
 						console.error(`Failed to convert shadow for thing ${thingName}`)
diff --git a/lwm2m/instanceTs.spec.ts b/lwm2m/instanceTs.spec.ts
new file mode 100644
index 0000000..e61073e
--- /dev/null
+++ b/lwm2m/instanceTs.spec.ts
@@ -0,0 +1,19 @@
+import { describe, it } from 'node:test'
+import assert from 'node:assert/strict'
+import { instanceTs } from './instanceTs.js'
+
+void describe('instanceTs()', () => {
+	void it('should return the timestamp of the instance', () =>
+		assert.equal(
+			instanceTs({
+				ObjectID: 14210,
+				ObjectVersion: '1.0',
+				Resources: {
+					'0': 3.5399999618530273,
+					'1': 4.168000221252441,
+					'99': '2024-02-23T10:18:20.474Z',
+				},
+			}).getTime(),
+			new Date('2024-02-23T10:18:20.474Z').getTime(),
+		))
+})
diff --git a/lwm2m/instanceTs.ts b/lwm2m/instanceTs.ts
new file mode 100644
index 0000000..eea05d4
--- /dev/null
+++ b/lwm2m/instanceTs.ts
@@ -0,0 +1,18 @@
+import {
+	type LwM2MObjectInstance,
+	definitions,
+	LwM2MObjectID,
+	timestampResources,
+} from '@hello.nrfcloud.com/proto-lwm2m'
+
+export const instanceTs = (instance: LwM2MObjectInstance): Date => {
+	const definition = definitions[instance.ObjectID as LwM2MObjectID]
+	const tsResourceId = timestampResources[definition.ObjectID] as number
+	const ts = instance.Resources[tsResourceId] as string
+	return new Date(ts)
+}
+
+export const newestInstanceFirst = (
+	i1: LwM2MObjectInstance,
+	i2: LwM2MObjectInstance,
+): number => instanceTs(i2).getTime() - instanceTs(i1).getTime()