diff --git a/ts/background.ts b/ts/background.ts
index 1ae6d91040..dd7ff439db 100644
--- a/ts/background.ts
+++ b/ts/background.ts
@@ -28,7 +28,7 @@ import { filter } from './util/iterables';
 import { isNotNil } from './util/isNotNil';
 import { senderCertificateService } from './services/senderCertificate';
 import { routineProfileRefresh } from './routineProfileRefresh';
-import { isMoreRecentThan, isOlderThan } from './util/timestamp';
+import { isMoreRecentThan, isOlderThan, toDayMillis } from './util/timestamp';
 import { isValidReactionEmoji } from './reactions/isValidReactionEmoji';
 import { ConversationModel } from './models/conversations';
 import { getMessageById } from './messages/getMessageById';
@@ -672,7 +672,7 @@ export async function startApp(): Promise<void> {
     webFrame.setZoomFactor(window.Events.getZoomFactor());
 
     // How long since we were last running?
-    const lastHeartbeat = window.storage.get('lastHeartbeat', 0);
+    const lastHeartbeat = toDayMillis(window.storage.get('lastHeartbeat', 0));
     const previousLastStartup = window.storage.get('lastStartup');
     await window.storage.put('lastStartup', Date.now());
 
@@ -685,10 +685,10 @@ export async function startApp(): Promise<void> {
     }
 
     // Start heartbeat timer
-    window.storage.put('lastHeartbeat', Date.now());
+    window.storage.put('lastHeartbeat', toDayMillis(Date.now()));
     const TWELVE_HOURS = 12 * 60 * 60 * 1000;
     setInterval(
-      () => window.storage.put('lastHeartbeat', Date.now()),
+      () => window.storage.put('lastHeartbeat', toDayMillis(Date.now())),
       TWELVE_HOURS
     );
 
diff --git a/ts/test-both/util/timestamp_test.ts b/ts/test-both/util/timestamp_test.ts
index 7ff94a41e9..f920da3be4 100644
--- a/ts/test-both/util/timestamp_test.ts
+++ b/ts/test-both/util/timestamp_test.ts
@@ -3,7 +3,11 @@
 
 import { assert } from 'chai';
 
-import { isOlderThan, isMoreRecentThan } from '../../util/timestamp';
+import {
+  isOlderThan,
+  isMoreRecentThan,
+  toDayMillis,
+} from '../../util/timestamp';
 
 const ONE_HOUR = 3600 * 1000;
 const ONE_DAY = 24 * ONE_HOUR;
@@ -34,4 +38,17 @@ describe('timestamp', () => {
       );
     });
   });
+
+  describe('toDayMillis', () => {
+    const now = new Date();
+    const today = new Date(toDayMillis(now.valueOf()));
+
+    assert.strictEqual(today.getUTCMilliseconds(), 0);
+    assert.strictEqual(today.getUTCHours(), 0);
+    assert.strictEqual(today.getUTCMinutes(), 0);
+    assert.strictEqual(today.getUTCSeconds(), 0);
+    assert.strictEqual(today.getUTCDate(), now.getUTCDate());
+    assert.strictEqual(today.getUTCMonth(), now.getUTCMonth());
+    assert.strictEqual(today.getUTCFullYear(), now.getUTCFullYear());
+  });
 });
diff --git a/ts/util/timestamp.ts b/ts/util/timestamp.ts
index 5fdf406ace..eb23eac6b1 100644
--- a/ts/util/timestamp.ts
+++ b/ts/util/timestamp.ts
@@ -1,6 +1,8 @@
 // Copyright 2021 Signal Messenger, LLC
 // SPDX-License-Identifier: AGPL-3.0-only
 
+const ONE_DAY = 24 * 3600 * 1000;
+
 export function isMoreRecentThan(timestamp: number, delta: number): boolean {
   return timestamp > Date.now() - delta;
 }
@@ -16,3 +18,7 @@ export function isInPast(timestamp: number): boolean {
 export function isInFuture(timestamp: number): boolean {
   return isMoreRecentThan(timestamp, 0);
 }
+
+export function toDayMillis(timestamp: number): number {
+  return timestamp - (timestamp % ONE_DAY);
+}