diff --git a/ui/src/ui/presenter.test.ts b/ui/src/ui/presenter.test.ts
new file mode 100644
index 00000000000..19e4f4d9ecf
--- /dev/null
+++ b/ui/src/ui/presenter.test.ts
@@ -0,0 +1,13 @@
+import { describe, expect, it } from "vitest";
+import { formatNextRun } from "./presenter.ts";
+
+describe("formatNextRun", () => {
+  it("returns n/a for Date-invalid finite timestamps", () => {
+    expect(formatNextRun(8_640_000_000_000_001)).toBe("n/a");
+  });
+
+  it("formats valid timestamps with weekday context", () => {
+    expect(formatNextRun(0)).toBe("n/a");
+    expect(formatNextRun(1_700_000_000_000)).toContain(",");
+  });
+});
diff --git a/ui/src/ui/presenter.ts b/ui/src/ui/presenter.ts
index c0e3c42a13d..95aa981400e 100644
--- a/ui/src/ui/presenter.ts
+++ b/ui/src/ui/presenter.ts
@@ -1,6 +1,7 @@
 import { t } from "../i18n/index.ts";
 import { resolveCronJobLastRunStatus } from "./cron-status.ts";
 import {
+  formatDateMs,
   formatRelativeTimestamp,
   formatDurationHuman,
   formatMs,
@@ -25,7 +26,10 @@ export function formatNextRun(ms?: number | null) {
   if (!ms) {
     return t("common.na");
   }
-  const weekday = new Date(ms).toLocaleDateString(undefined, { weekday: "short" });
+  const weekday = formatDateMs(ms, { weekday: "short" });
+  if (weekday === t("common.na")) {
+    return weekday;
+  }
   return `${weekday}, ${formatMs(ms)} (${formatRelativeTimestamp(ms)})`;
 }