diff --git a/frontend/app/javascript/shared/helpers/specs/timeHelper.spec.js b/frontend/app/javascript/shared/helpers/specs/timeHelper.spec.js
index 4bb12718..19240a25 100644
--- a/frontend/app/javascript/shared/helpers/specs/timeHelper.spec.js
+++ b/frontend/app/javascript/shared/helpers/specs/timeHelper.spec.js
@@ -6,6 +6,7 @@ import {
   shortTimestamp,
   getDayDifferenceFromNow,
   hasOneDayPassed,
+  isNewerTimestamp,
 } from 'shared/helpers/timeHelper';
 import { zhCN } from 'date-fns/locale';
 
@@ -20,6 +21,25 @@ afterEach(() => {
   vi.useRealTimers();
 });
 
+describe('#isNewerTimestamp', () => {
+  it.each([
+    ['Unix seconds', 1_700_000_000, 1_700_000_001],
+    ['numeric strings', '1700000000', '1700000001'],
+    ['early Unix milliseconds', 978_307_200_000, 1_700_000_000],
+    ['below the former 1e12 threshold', 999_999_999_999, 1_000_000_000_000],
+  ])('orders %s', (_label, current, next) => {
+    expect(isNewerTimestamp(current, next)).toBe(true);
+  });
+
+  it('preserves missing and invalid timestamp compatibility', () => {
+    expect(isNewerTimestamp(null, 'invalid')).toBe(true);
+    expect(isNewerTimestamp(1_700_000_000, null)).toBe(true);
+    expect(isNewerTimestamp('invalid', 1_700_000_000)).toBe(true);
+    expect(isNewerTimestamp(1_700_000_000, 'invalid')).toBe(false);
+    expect(isNewerTimestamp(1_700_000_000, 9e15)).toBe(false);
+  });
+});
+
 describe('#messageStamp', () => {
   it('returns correct value', () => {
     expect(messageStamp(1612971343)).toEqual('3:35 PM');
diff --git a/frontend/app/javascript/shared/helpers/timeHelper.js b/frontend/app/javascript/shared/helpers/timeHelper.js
index 3f02cb42..529340c1 100644
--- a/frontend/app/javascript/shared/helpers/timeHelper.js
+++ b/frontend/app/javascript/shared/helpers/timeHelper.js
@@ -6,11 +6,20 @@ import {
   differenceInDays,
 } from 'date-fns';
 
+// Numeric realtime timestamps below 1e10 are Unix seconds (through 2286-11-20);
+// larger values are milliseconds, bounded by the ECMAScript Date range.
+const UNIX_SECONDS_LIMIT = 1e10;
+const DATE_MILLISECONDS_LIMIT = 8.64e15;
+
 const normalizeTimestamp = value => {
   const numericValue =
     typeof value === 'string' && value.trim() ? Number(value) : value;
   if (typeof numericValue === 'number' && Number.isFinite(numericValue)) {
-    return Math.abs(numericValue) < 1e12 ? numericValue * 1000 : numericValue;
+    const timestamp =
+      Math.abs(numericValue) < UNIX_SECONDS_LIMIT
+        ? numericValue * 1000
+        : numericValue;
+    return Math.abs(timestamp) <= DATE_MILLISECONDS_LIMIT ? timestamp : null;
   }
   if (typeof value !== 'string') return null;