diff --git a/gui/src/components/QuotaBars.tsx b/gui/src/components/QuotaBars.tsx
index da782d0d02..5101a8eae5 100644
--- a/gui/src/components/QuotaBars.tsx
+++ b/gui/src/components/QuotaBars.tsx
@@ -341,9 +341,8 @@ function StackedQuotaRow({ row, threshold, t, locale, incomplete }: {
 }
 
 function formatResetAt(resetAt: number | undefined, t: TFn, locale: Locale): { day: string; time: string } {
-  if (typeof resetAt !== "number" || !Number.isFinite(resetAt)) return { day: "", time: "" };
-  const ms = resetAt < 10_000_000_000 ? resetAt * 1000 : resetAt;
-  const date = new Date(ms);
+  const date = resetAtDate(resetAt);
+  if (!date) return { day: "", time: "" };
   const now = new Date();
   const tag = bcp47(locale);
   const time = new Intl.DateTimeFormat(tag, { hour: "2-digit", minute: "2-digit", hour12: false }).format(date);
@@ -362,9 +361,9 @@ export function formatResetFuture(
   locale: Locale = "en",
   now = Date.now(),
 ): string {
-  if (typeof resetAt !== "number" || !Number.isFinite(resetAt)) return "";
-  const ms = resetAt < 10_000_000_000 ? resetAt * 1000 : resetAt;
-  const date = new Date(ms);
+  const date = resetAtDate(resetAt);
+  if (!date) return "";
+  const ms = date.getTime();
   const tag = bcp47(locale);
   const time = new Intl.DateTimeFormat(tag, { hour: "2-digit", minute: "2-digit", hour12: false }).format(date);
   const nowDate = new Date(now);
@@ -395,3 +394,10 @@ export function formatResetFuture(
 
   return t("quota.resetsAt", { date: dateStr, time, when: `${dateStr}, ${time}` });
 }
+
+function resetAtDate(resetAt: number | undefined): Date | null {
+  if (typeof resetAt !== "number" || !Number.isFinite(resetAt)) return null;
+  const milliseconds = resetAt < 10_000_000_000 ? resetAt * 1000 : resetAt;
+  const date = new Date(milliseconds);
+  return Number.isFinite(date.getTime()) ? date : null;
+}
diff --git a/gui/tests/intl-formatters.test.ts b/gui/tests/intl-formatters.test.ts
index fa38faace3..186abe2690 100644
--- a/gui/tests/intl-formatters.test.ts
+++ b/gui/tests/intl-formatters.test.ts
@@ -1,5 +1,7 @@
 import { describe, expect, test } from "bun:test";
 import { formatCreditDate, formatCreditDateTime } from "../src/intl-formatters";
+import { formatResetFuture } from "../src/components/QuotaBars";
+import type { TFn } from "../src/i18n";
 
 describe("credit date formatting", () => {
   test("keeps the compact date format for grant dates", () => {
@@ -22,3 +24,11 @@ describe("credit date formatting", () => {
     expect(formatCreditDateTime("invalid")).toBe("—");
   });
 });
+
+describe("quota reset formatting", () => {
+  test("ignores timestamps outside the JavaScript Date range", () => {
+    const t = ((key: string) => key) as TFn;
+
+    expect(formatResetFuture(1e20, t)).toBe("");
+  });
+});
diff --git a/src/codex/quota.ts b/src/codex/quota.ts
index 562e7082e3..e66ee3db01 100644
--- a/src/codex/quota.ts
+++ b/src/codex/quota.ts
@@ -152,6 +152,8 @@ function normalizeResetAt(value: unknown): number | undefined {
       ? Number(value)
       : undefined;
   if (typeof numeric !== "number" || !Number.isFinite(numeric) || numeric < 0) return undefined;
+  const milliseconds = numeric < 10_000_000_000 ? numeric * 1000 : numeric;
+  if (!Number.isFinite(new Date(milliseconds).getTime())) return undefined;
   return numeric;
 }
 
diff --git a/tests/rate-limit-reset-credits.test.ts b/tests/rate-limit-reset-credits.test.ts
index 122d78c01a..0030738902 100644
--- a/tests/rate-limit-reset-credits.test.ts
+++ b/tests/rate-limit-reset-credits.test.ts
@@ -34,6 +34,17 @@ describe("rate-limit reset credits", () => {
       expect(quota!.resetCredits).toBeUndefined();
     });
 
+    it("discards reset timestamps outside the JavaScript Date range", () => {
+      const quota = parseUsageQuota({
+        rate_limit: {
+          primary_window: { used_percent: 10, reset_at: 1e20 },
+          tertiary_window: { used_percent: 20, reset_at: 1e20 },
+        },
+      });
+
+      expect(quota).toEqual({ weeklyPercent: 10, monthlyPercent: 20 });
+    });
+
     it("handles credits-only response (no rate_limit)", () => {
       const data: WhamUsageResponse = {
         rate_limit_reset_credits: { available_count: 1 },