diff --git a/src/agents/current-time.test.ts b/src/agents/current-time.test.ts
new file mode 100644
index 00000000000..3abaafed3da
--- /dev/null
+++ b/src/agents/current-time.test.ts
@@ -0,0 +1,20 @@
+import { afterEach, describe, expect, it, vi } from "vitest";
+import { resolveCronStyleNow } from "./current-time.js";
+
+describe("resolveCronStyleNow", () => {
+  afterEach(() => {
+    vi.restoreAllMocks();
+  });
+
+  it("falls back when nowMs is outside Date range", () => {
+    vi.spyOn(Date, "now").mockReturnValue(Date.parse("2026-05-30T12:00:00.000Z"));
+
+    const result = resolveCronStyleNow(
+      { agents: { defaults: { userTimezone: "UTC", timeFormat: "24" } } },
+      8_640_000_000_000_001,
+    );
+
+    expect(result.formattedTime).toBe("Saturday, May 30th, 2026 - 12:00");
+    expect(result.timeLine).toContain("Reference UTC: 2026-05-30 12:00 UTC");
+  });
+});
diff --git a/src/agents/current-time.ts b/src/agents/current-time.ts
index f0de821e226..4d55a0a6527 100644
--- a/src/agents/current-time.ts
+++ b/src/agents/current-time.ts
@@ -1,3 +1,4 @@
+import { asDateTimestampMs } from "../shared/number-coercion.js";
 import {
   type TimeFormatPreference,
   formatUserTime,
@@ -23,9 +24,10 @@ type TimeConfigLike = {
 export function resolveCronStyleNow(cfg: TimeConfigLike, nowMs: number): CronStyleNow {
   const userTimezone = resolveUserTimezone(cfg.agents?.defaults?.userTimezone);
   const userTimeFormat = resolveUserTimeFormat(cfg.agents?.defaults?.timeFormat);
-  const formattedTime =
-    formatUserTime(new Date(nowMs), userTimezone, userTimeFormat) ?? new Date(nowMs).toISOString();
-  const utcTime = new Date(nowMs).toISOString().replace("T", " ").slice(0, 16) + " UTC";
+  const timestampMs = asDateTimestampMs(nowMs) ?? Date.now();
+  const date = new Date(timestampMs);
+  const formattedTime = formatUserTime(date, userTimezone, userTimeFormat) ?? date.toISOString();
+  const utcTime = date.toISOString().replace("T", " ").slice(0, 16) + " UTC";
   const timeLine = `Current time: ${formattedTime} (${userTimezone})\nReference UTC: ${utcTime}`;
   return { userTimezone, formattedTime, timeLine };
 }